#include<bits/stdc++.h>

using i64 = long long;
using l64 = long double;

std::mt19937_64 rng(std::chrono::system_clock::now().time_since_epoch().count());

void DAOQI() {
    int n;
    std::cin >> n;
    std::vector<i64> a(n + 1), p(n + 1);
    for (int i = 1; i <= n; i++) {
        std::cin >> a[i];
        p[i] = i;
    }

    for (int i = 1; i <= 500000; i++) {
        i64 sum = 0;
        for (int j = 1; j <= n / 2; j++) {
            sum += a[p[j]];
        }
        if (sum == 1e9) {
            std::cout << n / 2 << " ";
            for (int j = 1; j <= n / 2; j++) std::cout << p[j] << " ";
            return;
        }
        shuffle(p.begin() + 1, p.end(), rng);
    }
}

signed main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int T = 1;
    //std::cin >> T;
    while (T--) DAOQI();
    return 0;
}