...

#include<bits/stdc++.h>
using namespace std;
int p[100005];
int main(){
int n;
cin >> n;
p[1] = 1;
p[2] = 2;
p[3] = 4;
p[4] = 7;
p[5] = 12;
for(int i = 6;i <= n;i++) p[i] = p[i-1] + p[i-2] + p[i-4];
cout << p[n];
return 0;
}