In description of this problem you see that K <= 107, but it greater
even than 10007!!! To check this I used following code. Am I wrong?

  Program TopologicalSorting;
   Var N,M,K,I,Min       : Integer;
       A                 : Array [1 .. 10000] Of Integer;
       L,R               : Array [1 .. 1000]  Of Integer;

   Procedure QS(M,T : Integer);
    Var I,J,W,X : Integer;
    Begin
     I := M; J := T; X := A[Random(T - M) + M];
     Repeat
      While A[I] < X Do
       Inc(I);
      While A[J] > X Do
       Dec(J);
      If I <= J
       Then begin
             W := A[I]; A[I] := A[J]; A[J] := W;
             Inc(I); Dec(J);
            end;
     Until I > J;
     If I < T
      Then QS(I,T);
     If M < J
      Then QS(M,J);
    End;

   Procedure MakeFDBZ;
    Var A : Real;
    Begin
     A := 0;
     A := 1 / A;
    End;

   BEGIN
    Randomize;    {
    Assign(Input,'f.in');   Reset(Input);
    Assign(Output,'f.out'); ReWrite(Output);}
    Read(N,M,K);
    If (K > 1007)
     Then MakeFDBZ;
    N := N * M;
    For I := 1 To N Do
     begin
      Read(A[I]);
     end;
    QS(1,N);
    FillChar(L,SizeOf(L),0);
    FillChar(R,SizeOf(R),0);
    I := 1;
    While I <= N Do
     begin
      L[A[I]] := I;
      Inc(I);
      While (I <= N) And (A[I - 1] = A[I]) Do
       Inc(I);
      R[A[I - 1]] := I - 1;
     end;
    Min := 1;
    While L[Min] = 0 Do
     Inc(Min);
    For I := 1 To K Do
     begin
      Dec(R[Min]);
      L[Min + 1] := R[Min] + 1;
      If R[Min] < L[Min]
       Then Inc(Min);
     end;
    WriteLn(Min);{
    Close(Input);
    Close(Output);}
   END.

Note: 107 != 10^7