program tinhtong;
uses crt;
var i,n,s: integer;
begin
clrscr;
readln(n);
i:=0;
s:=0;
while i<= n do
begin
s:=s+i;
i:=i+1;
end;
Write('tong s la',s);
readln
end.
program tinhtich;
uses crt;
var i,n,tich: integer;
begin
clrscr;
readln(n);
i:=1;
tich:=1;
while i<=n do
begin
tich:= tich * i;
i:=i +1;
end;
readln
end.