#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint998244353;
//const int mod = 998244353;
//using mint = modint1000000007;
//const int mod = 1000000007;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
long long f(long long a, long long b) {
	long long g = gcd(a, b);
	if (1 != g)return 0;
	return (a - 1) * (b - 1);
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	vector<int>a(n);
	rep(i, n)cin >> a[i];
	if (3 != n) {
		rep(i, n - 1) {
			auto x = f(a[i * 2], a[i * 2 + 1]);
			a.push_back(x);
		}
		cout << a.back() << endl;
		rep(i, n - 1) {
			cout << 1 << " " << 2 << endl;
		}
		return 0;
	}
	auto x0 = f(f(a[0], a[1]), a[2]);
	auto x1 = f(f(a[0], a[2]), a[1]);
	auto x2 = f(f(a[1], a[2]), a[0]);
	auto mn = min({ x0,x1,x2 });
	if (x0 == mn) {
		cout << mn << endl;
		cout << 1 << " " << 2 << endl;
		cout << 1 << " " << 2 << endl;
	}
	else if (x1 == mn) {
		cout << mn << endl;
		cout << 1 << " " << 3 << endl;
		cout << 1 << " " << 2 << endl;
	}
	else {
		cout << mn << endl;
		cout << 2 << " " << 3 << endl;
		cout << 1 << " " << 2 << endl;
	}
	return 0;
}