#include<iostream> #include<cstdio> #include<cstring> #include<cmath> using namespace std; int shu(int a){ int c=1; for(int i=1;i<=a;i++){ c*=i; } return c; } int main(){ int n,y=0; cin>>n; for(int i=n;i>=1;i--){ y+=shu(i); } cout<<y<<endl; return 0; }