#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  VL a(n);
  rep(i, n) cin >> a[i];
  VI idx_odd, idx_even;
  rep(i, n) (a[i] % 2 ? idx_odd : idx_even).emplace_back(i);
  vector<P> ans;
  ll res = 0;
  auto f = [&](ll x, ll y) -> ll {
    if (x <= 1 || y <= 1) return 0;
    if (gcd(x, y) >= 2) return 0;
    return lcm(x, y) - x - y + 1;
  };
  if (idx_even.size() >= 2) {
    int i = idx_even[0], j = idx_even[1];
    ans.emplace_back(i, j);
    rep(i, n - 2) ans.emplace_back(0, n - 2 - i);
  } else if (idx_even.size() == 1 && idx_odd.size() >= 2) {
    int i = idx_even[0], j = idx_odd[0], k = idx_odd[1];
    ans.emplace_back(j, k);
    i -= (j < i) + (k < i);
    ans.emplace_back(i, n - 2);
    rep(i, n - 3) ans.emplace_back(0, n - 3 - i);
  } else if (idx_odd.size() >= 4) {
    int i1 = idx_odd[0], i2 = idx_odd[1], i3 = idx_odd[2], i4 = idx_odd[3];
    ans.emplace_back(i3, i4);
    ans.emplace_back(i1, i2);
    ans.emplace_back(n - 4, n - 3);
    rep(i, n - 4) ans.emplace_back(0, n - 4 - i);
  } else if (n == 3) {
    res = 1e18;
    auto op = [&](int i, int j) {
      ll x = f(a[3 - i - j], f(a[i], a[j]));
      if (chmin(res, x)) {
        ans.clear();
        ans.emplace_back(i, j);
        ans.emplace_back(0, 1);
      }
    };
    op(0, 1);
    op(0, 2);
    op(1, 2);
  } else {
    assert(n == 2);
    res = f(a[0], a[1]);
    ans.emplace_back(0, 1);
  }
  cout << res << '\n';
  for (auto [i, j] : ans) cout << i + 1 << ' ' << j + 1 << '\n';
}