krsu 860

/*
by: senb1 aka amigo
*/

#include <bits/stdc++.h>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
#define all(x) x.begin(), x.end()

const ll maxn = 26;
const ll inf = 1e9 + 6;
const ll mod = 1000;

int main() {
    std::ios::sync_with_stdio(0);
    std::cin.tie(0);

    int n;
    cin >> n;
    vector<vector<int>> dp(3, vector<int>(n + 1));
    dp[0][1] = 1;
    dp[0][2] = 3;
    dp[1][2] = 2;
    dp[2][2] = 1;
    for (int i = 3; i <= n; i++) {
        dp[0][i] = (dp[0][i - 1] + dp[1][i - 1] + dp[2][i - 1]) % mod;
        dp[1][i] = (dp[0][i - 1] + dp[0][i - 2]) % mod;
        dp[2][i] = dp[0][i - 1] % mod;
    }
    cout << (dp[0][n] + dp[1][n] + dp[2][n] - 1) % mod << endl;
}