program TinhTong;
uses crt;
var
N, i, j, tich: integer;
S: real;
begin
clrscr;
write('Nhap so nguyen N: ');
readln(N);
S := 0;
tich := 1;
for i := 1 to N do
begin
tich := tich * i;
S := S + tich;
end;
writeln('Tong S = ', S:0:2);
readln;
end.