*Bài tính S2:
---
Program BTT;
Uses crt;
Var S: extended;
i,n: longint;
Function GT(a: longint): int64;
Var i: longint; s: int64;
Begin
s:=1;
For i:=2 to a do
s:=s*i;
GT:=s;
End;
Begin
Clrscr;
Write('Nhap n: '); Readln(n);
s:=0;
For i:=1 to n do
s:=s+1/GT(i);
Write('S2 = ',s:0:2);
Readln
End.