哈~ 不过是单向广搜 慢了点啊
Const
        l=500;
        l2=10000;
        imp=10000000;
        a:array [0..4,0..1] of integer=((0,0),(1,0),(0,-1),(-1,0),(0,1));
Type
        jl=record
                x,y,f:longint;
        End;
Var
        i,j,k,m,n,head,last:longint;
        dx,df,dy,mx,my,uf,ux,uy:longint;
        stop:array [1..l,1..l] of boolean;
        indl:array [1..l,1..l,0..4] of boolean;
        step:array [1..l,1..l,0..4] of longint;
        easybroken:array [1..l,1..l] of boolean;
        dl:array [0..l2] of jl;

Procedure add(hx,hy,hf,hs:longint);
Var
        hx2,hy2,hf2:longint;
Begin
        step[hx,hy,hf] := hs;
        If not indl[hx,hy,hf] then Begin
                last := last+1;
                If last=l2 then last := 0;
                dl[last].x := hx;
                dl[last].y := hy;
                dl[last].f := hf;
                indl[hx,hy,hf] := true;
        End;
        hx2 := hx+a[hf,0];
        hy2 := hy+a[hf,1];
        Case hf of
                1:hf2 := 3;
                2:hf2 := 4;
                3:hf2 := 1;
                4:hf2 := 2;
                Else hf2 := 0;
        End;
        If hf2>0 then step[hx2,hy2,hf2] := hs;
End;

Procedure init;
Var
        s:ansistring;
        sx1,sy1,sf:longint;
Begin
        Readln(m,n);
        If m=0 then Halt;
        sx1 := 0;
        sy1 := 0;
        sf := 0;
        Fillchar(stop,sizeof(stop),0);
        Fillchar(indl,sizeof(indl),0);
        Fillchar(easybroken,sizeof(easybroken),0);
        Fillchar(dl,sizeof(dl),0);
        For i := 1 to m do For j := 1 to n do For k := 0 to 4 do step[i,j,k] := imp;
        For i := 1 to m do Begin
                Readln(s);
                For j := 1 to n do
                        Case s[j] of
                                '#':stop[i,j] := true;
                                'O':Begin
                                        mx := i;
                                        my := j;
                                End;
                                'X':Begin
                                        If sx1=0 then Begin
                                                sx1 := i;
                                                sy1 := j;
                                        End
                                        Else Begin
                                                If i>sx1 then sf := 1
                                                Else    If i<sx1 then sf := 3
                                                        Else    If j>sy1 then sf := 4
                                                                Else sf := 2;
                                        End;
                                End;
                                'E':easybroken[i,j] := true;
                        End;
        End;
        head := -1;
        last := -1;
        add(sx1,sy1,sf,0);
End;

Procedure bfs;
Var
        nowstep:longint;
        ux2,uy2:longint;
Begin
        While head<>last do Begin
                head := head+1;
                If head=l2 then head := 0;
                dx := dl[head].x;
                dy := dl[head].y;
                df := dl[head].f;
                nowstep := step[dx,dy,df];
                If df=0 then Begin
                        If (dx=mx)and(dy=my) then Continue;
                        For i := 1 to 4 do Begin
                                ux := dx+a[i,0];
                                uy := dy+a[i,1];
                                ux2 := ux+a[i,0];
                                uy2 := uy+a[i,1];
                                uf := i;
                                If (ux<1)or(uy<1)or(ux2<1)or(uy2<1)or(ux>m)or(ux2>m)or(uy>n)or(uy2>n) then Continue;
                                If (stop[ux,uy])or(stop[ux2,uy2]) then Continue;
                                If step[ux,uy,uf]<=nowstep+1 then Continue;
                                add(ux,uy,uf,nowstep+1);
                        End;
                End
                Else Begin
                        If df=3 then Begin
                                dx := dx+a[3,0];
                                dy := dy+a[3,1];
                                df := 1;
                        End;
                        If df=4 then Begin
                                dx := dx+a[4,0];
                                dy := dy+a[4,1];
                                df := 2;
                        End;
                        If df=1 then Begin
                                For i := 1 to 4 do Begin
                                        ux := dx+a[i,0];
                                        uy := dy+a[i,1];
                                        If i=df then Begin
                                                ux := ux+a[i,0];
                                                uy := uy+a[i,1];
                                        End;
                                        If (i=1)or(i=3) then Begin
                                                ux2 := ux;
                                                uy2 := uy;
                                                uf := 0;
                                        End
                                        Else Begin
                                                ux2 := ux+a[df,0];
                                                uy2 := uy+a[df,1];
                                                uf := df;
                                        End;
                                        If (ux<1)or(uy<1)or(ux2<1)or(uy2<1)or(ux>m)or(ux2>m)or(uy>n)or(uy2>n) then Continue;
                                        If (ux=ux2)and(uy=uy2)and(easybroken[ux,uy]) then Continue;
                                        If (stop[ux,uy])or(stop[ux2,uy2]) then Continue;
                                        If (step[ux,uy,uf]<=nowstep+1) then Continue;
                                        add(ux,uy,uf,nowstep+1);
                                End;
                        End
                        Else Begin
                                For i := 1 to 4 do Begin
                                        ux := dx+a[i,0];
                                        uy := dy+a[i,1];
                                        If i=df then Begin
                                                ux := ux+a[i,0];
                                                uy := uy+a[i,1];
                                        End;
                                        If (i=2)or(i=4) then Begin
                                                ux2 := ux;
                                                uy2 := uy;
                                                uf := 0;
                                        End
                                        Else Begin
                                                ux2 := ux+a[df,0];
                                                uy2 := uy+a[df,1];
                                                uf := df;
                                        End;
                                        If (ux<1)or(uy<1)or(ux2<1)or(uy2<1)or(ux>m)or(ux2>m)or(uy>n)or(uy2>n) then Continue;
                                        If (ux=ux2)and(uy=uy2)and(easybroken[ux,uy]) then Continue;
                                        If (stop[ux,uy])or(stop[ux2,uy2]) then Continue;
                                        If (step[ux,uy,uf]<=nowstep+1) then Continue;
                                        add(ux,uy,uf,nowstep+1);
                                End;
                        End;
                End;
                indl[dx,dy,df] := false;
        End;
End;


Begin
While true do Begin
        init;
        bfs;
        If step[mx,my,0]=imp then Writeln('Impossible')
        Else Writeln(step[mx,my,0]);
End;
End.