#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)



int N;
int g(int x) {
    if (x < 2) return 2;
    return (2 * g(x - 1) + 2 * g(x - 2)) % 1000;
}
//-----------------------------------------------------------------------------------
int main() {
    cin >> N;

    int ans = g(N);
    if (N % 2 == 0) ans = (ans - 1 + 1000) % 1000;
    cout << ans << endl;
}