#include<bits/stdc++.h> using namespace std; int main() { int n; long long f[100]; f[1] = 1; f[2] = 2; f[3] = 4; for(int i = 4; i <= 70; i ++) f[i] = f[i-1] + f[i-2] + f[i-3]; cin>>n; while(n) { cout<<f[n]<<endl; cin>>n; } return 0; }