Program PKU2507;
const
 zero=0.000000000001;
Var
 x,y,c:extended;
 f1,f2:text;
 ans:extended;
Procedure Init;
Begin
 read(f1,x,y,c);
 c:=1/c;
End;
Function Get(left,right:extended):extended;
Var
 t,k,a,b:extended;
Begin
 k:=(left+right)/2;
 a:=sqrt(sqr(x)-sqr(k));
 b:=sqrt(sqr(y)-sqr(k));
 t:=(a+b)/(a*b);
 if abs(t-c)<zero then Get:=k
 else if t-c<zero then Get:=Get(k,right)
 else if t-c>zero then Get:=Get(left,k);
End;
Function Get_Min(a,b:extended):extended;
Begin
 if a>b then Get_Min:=b
 else get_min:=a;
End;
Procedure Print;
Begin
writeln(f2,ans:0:3);
End;
Begin
 assign(f1,'input.in');
 assign(f2,'output.out');
 reset(f1);rewrite(f2);
 Repeat
 Init;
 ans:=get(0,Get_Min(x,y));
 Print;
 Until EOF(f1);
 close(f1);close(f2);
End.

问题出在哪里呢？样例和自己出的数据都过了。。。抑或是谁能给一下数据？