#include <bits/stdc++.h>
using namespace std;
#define int long long
#define x first
#define y second
#define LL long long
typedef pair<int,int> PII;
int dx[] = {-1, 1, 0, 0};
int dy[] = {0, 0, -1, 1};
const int N = 1e6 + 10, MOD = 1e9 + 10;
int a[N], f[N];
int n, m, res;


void solve()
{
    int n;
    cin >> n;
    f[0] = 1;
    for(int i = 1; i <= 3; i ++ )
    {
        for(int j = i; j <= n; j ++ )
            f[j] += f[j-i];
    }
    cout << f[n];

}
signed main()
{
    solve();
    return 0;
}