1 4#include<bits/stdc++.h> using namespace std; int main(){ unsigned long long a[100000]; int n,i; a[1]=1; a[2]=2; a[3]=4; a[9]=7; while(cin>>n){ a[i]=a[i-3]+a[i-2]+a[i-1]; cout<<a[n]<<endl; } return 0; }