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