#include<bits/stdc++.h> using namespace std; int main() { unsigned long long i=0,a[1010],n; a[1]=1;a[2]=2;a[3]=4; while(cin>>n){ for(i=4;i<=n;i++) { a[i]=a[i-3]+a[i-2]+a[i-1];} cout<<a[n]<<endl; } return 0; }