#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
long long a,b,cnt[71];
long long f(int a){
	if(a==1)return 1;
	if(a==2)return 2;
	if(a==3)return 4;
	if(cnt[a])return cnt[a];
	cnt[a]=f(a-1)+f(a-2)+f(a-3);
	return cnt[a];
}
int main(void){
	int x;
	cin>>x;
	while(x!=0){
		cout<<f(x)<<endl;
		cin>>x;
	}
	return 0;
}