#include<bits/stdc++.h> using namespace std; long long a[105]; int main(){ int n; cin >> n; a[1] = 1; a[2] = 2; a[3] = 4; a[4] = 7; for(int i = 5;i <= n;i++) a[i] = a[i-1] + a[i-2] + a[i-4]; cout << a[n]; return 0; }