#include <bits/stdc++.h>

using namespace std;

#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int) (x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;

void solve() {
    int n; cin >> n;
    vi a[2];
    rep(i, 0, n) {
        int x; cin >> x;
        a[x].push_back(i + 1);
    }
    rep(i, 0, 2) {
        cout << sz(a[i]) << "\n";
        rep(j, 0, sz(a[i])) {
            cout << a[i][j] << " \n"[j == sz(a[i]) - 1];
        }
    }
}

signed main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);

    solve();

    return 0;
}