#include<bits/stdc++.h>
using namespace std;
int dp[1000];
int countWays(int n){
	if(n==0) return 1;
	if(n==1) return 1;
	if(n==2) return 2;
	if(n==3) return 4;
	vector<int> dp(n+1,0);
	dp[0] = 1;
	dp[1] = 1;
	dp[2] = 2;
	dp[3] = 4;
	
	for(int i=4; i<=n;i++){
		dp[i] = dp[i-1]+dp[i-2]+dp[i-3];
	}
	return dp[n];
}
int main(){
	int n;
	while(cin>>n&&n!=0){
		cout<<countWays(n)<<endl;
	}
	return 0;
}