#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <unordered_map>
#include <unordered_set>
 
#define REP(i, n) for(int (i) = 0; (i) < (n); (i)++)
#define SZ(a) (int)(a).size()
#define ALL(a) (a).begin(), (a).end()
 
using namespace std;

long long sum(const vector<int>& a, const vector<int>& idx) {
    long long sum = 0;
    REP(i, SZ(idx)) {
        sum += a[idx[i] - 1];
    }
    return sum;
}

bool isprime(int n) {
    if (n <= 1) return false;
    for (int i = 2; i * i <= n; i++) {
        if (n % i == 0) {
            return false;
        }
    }
    return true;
}

vector<int> run(const vector<int>& a, const int M) {
    const int n = SZ(a);
    vector<vector<bool>> dp(n + 1, vector<bool>(M));
    vector<vector<int>> pr(n + 1, vector<int>(M, -1));
    dp[0][0] = true;
    REP(i, n) {
        REP(j, M) {
            if (!dp[i][j]) {
                continue;
            }
            dp[i + 1][j] = true;
            pr[i + 1][j] = j;
            dp[i + 1][(j + a[i]) % M] = true;
            pr[i + 1][(j + a[i]) % M] = j;
        }
    }
    const int SUM = 1e9;
    vector<int> res;
    int cur = SUM % M;
    for (int i = n; i > 0; i--) {
        int prv = pr[i][cur];
        if (prv != cur) {
            res.push_back(i);
        }
        cur = prv;
    }
    return res;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    cin >> n;
    vector<int> a(n);
    REP(i, n) cin >> a[i];
    for (int M = 1000; ; M++) {
        if (isprime(M)) {
            vector<int> ids = run(a, M);
            if (sum(a, ids) == 1'000'000'000) {
                cout << SZ(ids) << '\n';
                for (int id : ids) cout << id << ' ';
                cout << '\n';
                return 0;
            }
        }
    }
    return 0;
}