type el = ^t;
     t = record
          link : el;
          val : longint;
         end;


var a : array[0..2000] of pointer;
    i, j, k, l, o, m, n, pp1, pp2 : longint;
    p, q : el;
    s, s1, st, msg, p1, p2 : string;
    int : integer;
    f : text;


begin
 assign(f, '');
 reset(f);
 readln(f, n);
 for i := 1 to n do
   begin
    readln(f, s);
    msg := '';
    p1 := '';
    p2 := '';
    while s[1] <> ' ' do
      begin
       msg := msg + s[1];
       delete(s, 1, 1);
      end;
    while s[1] = ' ' do
      delete(s, 1, 1);
    while (s[1] >= '0') and (s[1] <= '9') and (s <> '') do
      begin
       p1 := p1 + s[1];
       delete(s, 1, 1);
      end;
    if msg = 'PUSH' then
      begin
       while s[1] = ' ' do
         delete(s, 1, 1);
       while (s[1] >= '0') and (s[1] <= '9') and (s <> '') do
         begin
          p2 := p2 + s[1];
          delete(s, 1, 1);
         end;
      end;
    val(p1, pp1, int);
    if msg = 'PUSH' then val(p2, pp2, int);
    if msg = 'POP' then
      begin
       p := a[pp1];
       writeln(p^.val);
       a[pp1] := p^.link;
      end
    else
      begin
       new(p);
       p^.val := pp2;
       p^.link := a[pp1];
       a[pp1] := p;
      end;
   end;
 close(f);
end.

I ALSO HAD THIS PROBLEM, YOU SHOULD USE CHAR NOT STRING