My Email : caa@baga.ac.net.ru
=-=-=-=-=
Program acm_1126;

Var A            : array [1..25000] of longint;
    G            : array [0..400,0..299] of longint;
    Nums         : array [0..400] of longint;
    i,j,k        : longint;
    M,N          : longint;

Begin
  FillChar(G,sizeOf(G),0); FillChar(Nums,sizeOf(Nums),0);

  Read(M);

  i:=0; N:=0;
  While i<>-1 do BegiN
    Read(i);
    If i<>-1 then Begin
      Inc(N); A[N]:=i;
    End;
  End;

  For i:=1 to N do Begin
    j:=A[i] div 300; k:=A[i] mod 300; Inc(G[j,k]); Inc(Nums[j]);

    If i>M then Begin
      j:=A[i-M] div 300; k:=A[i-M] mod 300; Dec(G[j,k]); Dec(Nums[j]);
    End;

    If i>=M then Begin
      k:=400; While Nums[k]=0 do Dec(k);
      j:=299; While G[k,j]=0 do Dec(j);
      writeln(300*k+j);
    End;
  End;
End.

Read this program more clear again!