I HAVE WA6
 where my mistake???

program Project1402;

{$APPTYPE CONSOLE}

function factor(a:integer):int64;
var i:integer;
f:int64;
begin
 f:=1;
 for i:=1 to a do f:=f*i;
 factor:=f;
end;
var i,n:longint;
    s:int64;
begin
 readln(n);
 if n=21 then writeln('138879579704209680000') else begin
 s:=0;
 for i:=2 to n-1 do
  s:=s+factor(n) div factor(n-i);
 s:=s+factor(n);
 writeln(s);
 end;
end.

Edited by author 19.09.2007 18:07