#include <iostream> using namespace std; int main() { long long dp[72] = {0, 1, 2, 4}; for (int i = 4; i <= 71; ++i) { dp[i] = dp[i-1] + dp[i-2] + dp[i-3]; } int n; while (cin >> n && n != 0) { cout << dp[n] << endl; } return 0; }