#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <cmath>
#include <iomanip>
#include <stack>
#include <queue>
#include <numeric>
#include <map>
#include <unordered_map>
#include <set>
#include <fstream>
#include <chrono>
#include <random>
#include <bitset>
#include <atcoder/all>
#define rep(i,n) for(int i=0;i<(n);i++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) ((int)(x).size())
#define pb push_back
using ll = long long;
using namespace std;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
ll gcd(ll a, ll b) {return b?gcd(b,a%b):a;}
ll lcm(ll a, ll b) {return a/gcd(a,b)*b;}

ll f(ll a, ll b){
  ll g = gcd(a,b);
  if(g!=1){
    return 0;
  }
  return (a-1)*(b-1);
}

int main(){
  int N; cin >> N;
  vector<ll> A(N); rep(i,N) cin >> A[i];
  if(N==2){
    ll g = gcd(A[0],A[1]);
    if(g!=1){
      cout << 0 << '\n';
    }
    else{
      cout << (A[0]-1)*(A[1]-1) << '\n';
    }
    cout << "1 2\n"; 
  }
  else if(N==3){
    ll a012 = f(A[2],f(A[0],A[1]));
    ll a021 = f(A[1],f(A[0],A[2]));
    ll a120 = f(A[0],f(A[1],A[2]));
    ll mn = min({a012,a021,a120});
    cout << mn << '\n';
    if(mn==a012){
      cout << "1 2\n";
    }
    else if(mn==a021){
      cout << "1 3\n";
    }
    else{
      cout << "2 3\n"; 
    }
    cout << "1 2\n";
  }
  else{
    cout << 0 << '\n';
    rep(i,N-1){
      cout << "1 2\n";
    }
  }
  return 0;
}