#include <bits/stdc++.h>
using namespace std;
int giaithua(int n )
{
int temp = 1;
for (int i = 1; i <= n; i ++) temp *=i;
return temp;
}
int main()
{
int n;
cout << "Nhap n: "; cin >> n; cout << endl;
int tong = 1;
for (int i = 1; i <=n; i++) tong += 1/giaithua(i);
cout << "KQ la: " << tong;
return 0;
}