#include <iostream>
#include <vector>
#include <unordered_map>
#include <algorithm>
#include <map>

using namespace std;

int main() {
    int N;
    cin >> N;
    vector<int> c(N);
    for (int i = 0; i < N; ++i) {
        cin >> c[i];
    }

    const int64_t TARGET = 1e9;
    const int K = 100000; // Limit the number of sums to keep

    // Initialize sums
    map<int64_t, vector<int>> sums;
    sums[0] = {};

    for (int i = 0; i < N; ++i) {
        map<int64_t, vector<int>> next_sums = sums;

        for (auto& [s, idx_list] : sums) {
            int64_t s_new = s + c[i];
            if (s_new > TARGET) continue;

            if (s_new == TARGET) {
                // Found the solution
                idx_list.push_back(i + 1); // +1 because indices are 1-based
                cout << idx_list.size();
                for (int idx : idx_list) {
                    cout << " " << idx;
                }
                cout << endl;
                return 0;
            }

            if (next_sums.find(s_new) == next_sums.end() || next_sums[s_new].size() > idx_list.size() + 1) {
                vector<int> new_idx_list = idx_list;
                new_idx_list.push_back(i + 1); // +1 because indices are 1-based
                next_sums[s_new] = new_idx_list;
            }
        }

        // Prune the next_sums if it exceeds size K
        if (next_sums.size() > K) {
            // Keep only K smallest sums
            while (next_sums.size() > K) {
                next_sums.erase(prev(next_sums.end()));
            }
        }

        sums = move(next_sums);
    }

    // If we reach here, no exact sum was found
    // Optionally, output an approximate solution or indicate no solution
    cout << "0" << endl;
    return 0;
}