// PR Bab 13, soal 1 -- pembahasan.

#include <iostream>
using namespace std;

const int MOD = 1000000007;
const int MAKS = 1000005;
long long dp[MAKS];

int main() {
    int n;
    cin >> n;

    dp[0] = 1;
    if (n >= 1) dp[1] = 1;
    if (n >= 2) dp[2] = 2;                 // 1+1 atau 2

    for (int i = 3; i <= n; i++)
        dp[i] = (dp[i - 1] + dp[i - 2] + dp[i - 3]) % MOD;

    cout << dp[n] << "\n";
    return 0;
}