#include<iostream>
#include<cstdio>
using namespace std;
#define int long long 
const int N = 77;
int n, _f[N];
int f(int k)
{
    if(k == 1 || k == 2) return k;
    if(k == 3) return 4;
    if(_f[k]) return _f[k];
    return _f[k] = f(k - 1) + f(k - 2) + f(k - 3);
}
signed main(void)
{
    ios::sync_with_stdio(0);
    cin >> n;
    while(n)
    {
        cout << f(n) << endl;
        cin >> n;
    }
    return 0;
}