#include<bits/stdc++.h> using namespace std; int main(){ int n,a[100],i 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; }