#include <bits/stdc++.h>
using namespace std;
const int MOD=1e9+7;
int main(){
    int n; cin>>n;
    long long dp[n+1];
    dp[0]=1; dp[1]=1; dp[2]=2;
    for (int i = 3; i <= n; ++i) dp[i]=(dp[i-1]+dp[i-2]+dp[i-3])%MOD;
    cout<<dp[n];
    return 0;
}