#include<bits/stdc++.h>
using namespace std;

//* ATCODER
#include<atcoder/all>
using namespace atcoder;
typedef modint998244353 mint;
//*/

/* BOOST MULTIPRECISION
#include<boost/multiprecision/cpp_int.hpp>
using namespace boost::multiprecision;
//*/

typedef long long ll;

#define rep(i, s, n) for (int i = (int)(s); i < (int)(n); i++)
#define rrep(i, s, n) for (int i = (int)(n)-1; i >= (int)(s); i--)

template <typename T> bool chmin(T &a, const T &b) {
	if (a <= b) return false;
	a = b;
	return true;
}

template <typename T> bool chmax(T &a, const T &b) {
	if (a >= b) return false;
	a = b;
	return true;
}

template <typename T> T max(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmax(ret, a[i]);
	return ret;
}

template <typename T> T min(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmin(ret, a[i]);
	return ret;
}

template <typename T> T sum(vector<T> &a){
	T ret = 0;
	for (int i=0; i<(int)a.size(); i++) ret += a[i];
	return ret;
}

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

	auto f = [&](ll x, ll y) -> ll {
		if (x == 1 || y == 1){
			return 0;
		}
		if (x == 0 || y == 0){
			return 0;
		}
		if (__gcd(x, y) != 1){
			return 0;
		}
		return (x-1) * (y-1);
	};

	int n; cin >> n;
	vector<ll> a(n);
	rep(i,0,n){
		cin >> a[i];
	}

	if (n == 2){
		cout << f(a[0], a[1]) << '\n';
		cout << 1 << ' ' << 2 << '\n';
		return 0;
	}else if (n == 3){
		if (
			f(a[0], f(a[1], a[2])) >= f(a[2], f(a[0], a[1]))
		 && f(a[1], f(a[0], a[2])) >= f(a[2], f(a[0], a[1]))
		){
			cout << f(a[2], f(a[0], a[1])) << '\n';
			cout << 1 << ' ' << 2 << '\n';
			cout << 1 << ' ' << 2 << '\n';
		}else if (
			f(a[1], f(a[0], a[2])) >= f(a[0], f(a[1], a[2]))
		 && f(a[2], f(a[0], a[1])) >= f(a[0], f(a[1], a[2]))
		){
			cout << f(a[0], f(a[1], a[2])) << '\n';
			cout << 2 << ' ' << 3 << '\n';
			cout << 1 << ' ' << 2 << '\n';
		}else{
			cout << f(a[1], f(a[0], a[2])) << '\n';
			cout << 1 << ' ' << 3 << '\n';
			cout << 1 << ' ' << 2 << '\n';
		}
		return 0;
	}else{
		// 確実に 1, 0 のいずれかになる
		vector<pair<int,int>> ans;
		ans.push_back(pair(1, 2));
		ans.push_back(pair(1, 2));
		{
			vector<ll> newvec(n-1);
			rep(i,2,n){
				newvec[i-2] = a[i];
			}
			newvec[n-2] = f(a[0], a[1]);
			a = newvec;
		}
		{
			vector<ll> newvec(n-2);
			rep(i,2,n-1){
				newvec[i-2] = a[i];
			}
			newvec[n-3] = f(a[0], a[1]);
			a = newvec;
		}
		{
			int piv = n-4;
			ll v = f(a[n-4], a[n-3]);
			ans.push_back(pair(piv + 1, piv + 2));
			piv--;
			while(piv >= 0){
				v = f(v, a[piv]);
				ans.push_back(pair(piv + 1, piv + 2));
				piv--;
			}
			cout << v << '\n';
		}
		assert((int)ans.size() == n-1);
		rep(i,0,n-1){
			cout << ans[i].first << ' ' << ans[i].second << '\n';
		}
		

	}

}