#include<bits/stdc++.h> using namespace std; int main(){ unsigned long long n,a[100],i; a[1]=1,a[2]=2,a[3]=4,a[4]=7; 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; }