#include<iostream>
#include<cstring>
using namespace std;


int ans;
int n;

void dfs(int u)
{
    if(u == n) ans ++;
    if(u > n) return;

    dfs(u+1),dfs(u + 2),dfs(u + 3);
}
int main()
{

    cin >> n;
    dfs(0);
    cout << ans << endl;
    return 0;
}