#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 998244353;
// constexpr int MOD = 1000000007;
constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1};
constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U>
inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U>
inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

ll f(const ll i, const ll j) {
  return gcd(i, j) == 1 ? (i - 1) * (j - 1) : 0;
}

int main() {
  constexpr int A = 200000;
  int n; cin >> n;
  vector<int> a(n); REP(i, n) cin >> a[i];
  vector<pair<int, int>> ans;
  const auto finish = [&]() -> void {
    const int m = n - ans.size();
    for (int i = m - 1; i >= 1; --i) {
      ans.emplace_back(i - 1, i);
    }
    cout << 0 << '\n';
    for (const auto& [i, j] : ans) cout << i + 1 << ' ' << j + 1 << '\n';
    exit(0);
  };
  REP(i, n) {
    if (a[i] == 0 || a[i] == 1) {
      ans.emplace_back(i, (i + 1) % n);
      finish();
    }
  }
  array<int, A + 1> indices{};
  fill(indices.begin(), indices.end(), -1);
  REP(i, n) {
    if (indices[a[i]] != -1) {
      ans.emplace_back(indices[a[i]], i);
      finish();
    }
    indices[a[i]] = i;
  }
  for (int d = 2; d <= A; ++d) {
    int memo = -1;
    for (int i = d; i <= A; i += d) {
      if (memo == -1) {
        memo = indices[i];
      } else if (memo != -1 && indices[i] != -1) {
        ans.emplace_back(memo, indices[i]);
        finish();
      }
    }
  }
  vector<int> odd;
  REP(i, n) {
    if (a[i] % 2 == 1) odd.emplace_back(i);
  }
  if (odd.size() >= 4) {
    odd.resize(4);
    ans.emplace_back(odd.front(), odd[1]);
    ans.emplace_back(odd.end()[-2], odd.back());
    ans.emplace_back(n - 4, n - 3);
    finish();
  }
  if (n == 2) {
    cout << f(a.front(), a.back()) << '\n'
         << 1 << ' ' << 2 << '\n';
    return 0;
  }
  if (n == 4) {
    assert(odd.size() == 3);
    ans.emplace_back(odd.front(), odd[1]);
    a.erase(next(a.begin(), odd[1]));
    a.erase(next(a.begin(), odd.front()));
    a.emplace_back(f(a[odd.front()], a[odd[1]]));
    REP(i, a.size()) FOR(j, i + 1, a.size()) {
      if (a[i] % 2 == 0 && a[j] % 2 == 0) {
        ans.emplace_back(i, j);
        finish();
      }
    }
  }
  assert(n == 3);
  ll v = LINF;
  REP(i, n) FOR(j, i + 1, n) {
    const int k = i ^ j ^ 0 ^ 1 ^ 2;
    if (chmin(v, f(f(a[i], a[j]), a[k]))) ans = {{i, j}, {0, 1}};
  }
  cout << v << '\n';
  for (const auto& [i, j] : ans) cout << i + 1 << ' ' << j + 1 << '\n';
  return 0;
}