#include <bits/stdc++.h>
#define dd(x) cout << #x << "\n"
#define d(x) cout << #x  << ": " << x << "\n"
using namespace std;
#define int long long
using pii = pair<int, int>;
using vpii = vector<pii>;
using vi = vector<int>;
using vii = vector<vector<int>>;
using a3 = array<int, 3>;
using ll = long long;
const int inf = 0x3f3f3f3f3f3f3f3fLL;

const int mod = 6400;

void solve() {
    int n; cin >> n;
    vector<int> ori(n + 1);
    vector<pair<int, int>> a(n + 1);
    for(int i = 1; i <= n; i++) {
        cin >> ori[i];
        a[i].first = ori[i] % mod;
        a[i].second = i;
    }

    if(n == 2) {
        cout << (ll) 1e9 << "\n";
        return ;
    }

    vector<int> ans;
    mt19937 rng(19260817);
    auto check = [&]() {
        shuffle(a.begin() + 1, a.end(), rng);
        vector dp(mod + 1, vector<int>());
        ans.clear();
        int sum = 0;

        for(int i = 1; i <= n; i++) {
            vector<int> mdf(mod, 0);
            for(int j = mod - 1; j; j--) {
                if(dp[j].size() && !mdf[j]) {
                    if((j + a[i].first) % mod == 0) {
                        ans = dp[j];
                        ans.push_back(a[i].second);
                        goto end;
                    } else {
                        int id = (j + a[i].first) % mod;
                        dp[id] = dp[j];
                        dp[id].push_back(a[i].second);
                        mdf[id] = 1;
                    }
                }
            }
            dp[a[i].first] = vector<int>{a[i].second};
        }

        end:
        for(auto i : ans) {
            sum += ori[i];
        }

        if(sum != (long long)1e9) {
            return false;
        }
        return true;
    };

    while(!check()) {
        continue;
    }

    cout << ans.size() << " ";
    for(auto i : ans) {
        cout << i << " ";
    }
    cout << "\n";
}

signed main() {
    ios::sync_with_stdio(false); cin.tie(0);
    int T = 1;
    while(T--) solve();
    return 0;
}

/*

10
386413329 88494216 245947398 316438989 192751270 204627269 65749456 3938400 150458676 345180997

*/