#include <iostream>
using namespace std;
long long n;
signed main(){
	while(cin >> n)
		if(n==0LL || n==1LL)	printf("1\n");
		else printf("%lld\n", 1+n*(n-1)/2+n*(n-1)*(n-2)*(n-3)/4/3/2/1);
    return 0;
}

9行过what can I say?