#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second
mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
const ll MOD1000000007 = 1000000007;
const ll MOD998244353 = 998244353;
const ll MOD[3] = {999727999, 1070777777, 1000000007};
const ll LINF = 1LL << 60LL;
const int IINF = (1 << 30) - 1;


void solve(){
    ll n; cin >> n;
    vector<ll> a(n); rep(i, n) cin >> a[i];

    if(n==2){
        if(a[0]==0||a[1]==0){
            cout << 0 << endl;
        }else if(__gcd(a[0], a[1])!=1){
            cout << 0 << endl;
        }else{
            cout << (a[0]-1)*(a[1]-1) << endl;
        }
        cout << 1 << " " << 2 << endl;
        return;
    }

    if(n==3){
        if(a[0]==0||a[1]==0||a[2]==0){
            cout << 0 << endl;
            cout << 1 << " " << 2 << endl;
            cout << 1 << " " << 2 << endl;
            return;
        }

        vector<pll> b(3);
        rep(i, 3) b[i] = {a[i], i+1};
        sort(all(b));

        ll ans;
        if(__gcd(b[0].fi, b[1].fi)==1) ans = (b[0].fi-1)*(b[1].fi-1);
        else ans = 0;

        if(__gcd(ans, b[2].fi)!=1 || ans==0) ans = 0;
        else ans = (ans-1)*(b[2].fi-1);

        assert(false);

        cout << ans << endl;
        cout << b[0].se << " " << b[1].se << endl;
        cout << 1 << " " << 2 << endl;
        return;
    }

    //後ろ4つを処理
    cout << 0 << endl;
    cout << n-1 << " " << n << endl;
    cout << n-3 << " " << n-2 << endl;
    cout << n-3 << " " << n-2 << endl;
    for(ll i=n-4; i>=1; i--) cout << i << " " << i+1 << endl;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    int T=1;
    //cin >> T;
    while(T--) solve();
}