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#include <iostream>

using namespace std;

const int MAXN = 1e6 + 5;
int deg[MAXN];
int n;

bool find() {
    for (int i = 1; i <= n; i++) {
        if (deg[i]) {
            deg[i]--;
            return i != 1;
        }
    }
    return 0;
}

int main() {

    ios_base::sync_with_stdio(0);
    cin.tie(0);

    cin >> n;
    for (int i = 1; i <= n; i++) {
        int d;
        cin >> d;
        deg[d]++;
    }
    int x = 0, k = 2;
    if (find()) x++;
    if (find()) x++;

    cout << x << "\n" << k << "\n" << 1 << " " << 2 << "\n";
}