#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define X first
#define Y second
#define SZ(a) ((int)a.size())
#define ALL(v) v.begin(), v.end()
#define pb push_back

const ll INF = 9e18;

ll f(ll p, ll q) {
    if (p == 0 && q == 0) return 0;
    if (gcd(p, q) == 1) return p * q - p - q + 1;
    return 0;
}

int main() {
    ios::sync_with_stdio(0), cin.tie(0);
    int n;
    cin >> n;
    ll best_v = INF;
    vector<pii> ans;
    vector<ll> arr(n);
    for (ll &i : arr)
        cin >> i;

    auto op = [&](int a, int b) {
        ans.pb(pii(a + 1, b + 1));
        if (a > b) swap(a, b);
        ll res = f(arr[a], arr[b]);
        arr.erase(arr.begin() + b);
        arr.erase(arr.begin() + a);
        arr.pb(res);
    };

    if (SZ(arr) <= 3) {
        vector<pii> best_ans;
        auto _dfs = [&](auto dfs) {
            if (SZ(arr) == 1) {
                if (best_v > arr[0]) 
                    best_v = arr[0], best_ans = ans;
                return;
            }
            vector<ll> tmp = arr;
            for (int i = 0; i < SZ(arr); ++i)
                for (int j = i + 1; j < SZ(arr); ++j) {
                    op(i, j);
                    dfs(dfs);
                    arr = tmp, ans.pop_back();
                }
        };
        _dfs(_dfs);
        ans.swap(best_ans); 
    }
    else {
        while (true) {
            vector<int> even, odd;
            for (int i = 0; i < SZ(arr); ++i)
                if (arr[i] % 2 == 0) 
                    even.pb(i);
                else
                    odd.pb(i);
            if (SZ(even) >= 2) {
                op(even[SZ(even) - 2], even.back());
                break;
            }
            else
                op(odd[SZ(odd) - 2], odd.back());
        }
        assert(arr.back() == 0);
        while (SZ(arr) > 1) {
            op(SZ(arr) - 2, SZ(arr) - 1);
        }
        best_v = 0;
    }
    cout << best_v << "\n";
    for (auto [a, b] : ans)
        cout << a << " " << b << "\n";
}