#include <string>
#include <iostream>
#include <cmath>
using namespace std;

int mod = 1000000007;
int n;
int ans[1000006];

int main()
{
	cin >> n;

	ans[0] = 0;
	ans[1] = 1;
	ans[2] = 2;

	for (int i = 3; i <= n; i++) {
		ans[i] = (((ans[i - 1] + ans[i - 2]) % mod) + ans[i - 3]) % mod;
	}

	cout << ans[n] << endl;

	return 0;
}