希望大家指点……
发个甲骨文……

program asdf;
  type
    arr=record
      d,l,c:longint;
  end;
  var
    sum,n,m,ansl:longint;
    d:array[0..20000] of arr;
    ff:array[0..20000] of boolean;
    first,next:array[0..20000] of longint;
  procedure init;
    var
      i,s,e,l,t:longint;
    begin
      readln(sum);
      readln(n);
      readln(m);
      fillchar(d,sizeof(d),0);
      fillchar(first,sizeof(first),0);
      fillchar(next,sizeof(next),0);
      for i:=1 to m do
        begin
          readln(s,e,l,t);
          if t>sum then
            continue;
          next[i]:=first[s];
          d[i].d:=e;
          d[i].l:=l;
          d[i].c:=t;
          first[s]:=i;
        end;
    end;
  procedure sss(x,len,co:longint);
    var
      y,i,l,c:longint;
    begin
      if len>ansl then
        exit;
      if co>sum then
        exit;
      if x=n then
        begin
          if len<ansl then
            ansl:=len;
          exit;
        end;
      i:=first[x];
      while i<>0 do
        begin
          y:=d[i].d;
          l:=d[i].l;
          c:=d[i].c;
          if (c+co>sum)or(ff[y]) then
            begin
              i:=next[i];
              continue;
            end;
          ff[y]:=true;
          sss(y,len+l,co+c);
          ff[y]:=false;
          i:=next[i];
        end;
    end;
  procedure main;
    begin
      fillchar(ff,sizeof(ff),0);
      ff[1]:=true;
      ansl:=maxlongint;
      sss(1,0,0);
      if ansl<100000 then
        writeln(ansl)
      else writeln('-1');
    end;
  begin
    init;
    main;
  end.