procedure InitLongNumber(n: longint; var a: longnum); var i: longint; begin for i := 1 to len do if n <> 0 then begin a[i] := n mod 10; n := n div 10 end else a[i] := 0; end;
function mul(a: longnum; k: longint): longnum; var i, tmp: longint; begin tmp := 0;
for i := 1 to len - 1 do begin a[i] := a[i] * k + tmp; tmp := a[i] div 10; a[i] := a[i] mod 10 end;
result := a end;
procedure PrintLongNumber(a: longnum); var i, j: longint; begin i := len; while a[i] = 0 do dec(i); for j := i downto 1 do write(a[j]) end;
begin readln(n); InitLongNumber(1, s); for i := 1 to n do s := mul(s, i); write(n, '! = '); PrintLongNumber(s); end.
