#include <bits/stdc++.h>
const long double pi = 3.141592653589793116;
using namespace std;
long long power(long long a, long long p, long long m = 1000000007) {
  long long res = 1;
  while (p > 0) {
    if (p & 1) res = (res * a) % m;
    a = (a * a) % m;
    p >>= 1;
  }
  return res;
}
string to_binary(long long num) {
  string s;
  while (num) s.push_back(char(num & 1) + '0'), num >>= 1;
  reverse(s.begin(), s.end());
  return s;
}
void func() {
  long long n;
  cin >> n;
  long long arr[n + 1];
  for (int i = 1; i <= (n); i++) cin >> arr[i];
  map<long long, vector<long long>> m;
  for (int i = 1; i <= (n); i++) m[arr[i]].push_back(i);
  set<long long> p;
  map<long long, long long> sol;
  for (long long i = n; i >= 1; i--) {
    if (i == n) {
      sol[n] = 1;
      continue;
    }
    auto it = m.lower_bound(arr[i] + 1);
    if (it == m.end() || it->first != arr[i] + 1)
      sol[i] = 1;
    else {
      auto ptr = lower_bound(it->second.begin(), it->second.end(), i + 1);
      if (ptr == it->second.end())
        sol[i] = 1;
      else
        sol[i] = sol[*ptr] + 1;
    }
  }
  long long ans = 1;
  long long st = 0;
  for (int i = 1; i <= (n); i++) {
    auto it = m.lower_bound(arr[i] + 1);
    if (it == m.end() || it->first != arr[i] + 1) {
      continue;
    } else {
      auto ptr = lower_bound(it->second.begin(), it->second.end(), i + 1);
      if (ptr != it->second.end()) {
        if (sol[*ptr] + 1 > ans) {
          ans = max(ans, sol[*ptr] + 1);
          st = i;
        }
      }
    }
  }
  if (ans == 1) {
    cout << 1 << endl << 1 << endl;
  } else {
    vector<long long> tmp;
    tmp.push_back(st);
    long long i = st + 1;
    while (i <= n) {
      if (arr[i] == arr[st] + 1) {
        st = i;
        tmp.push_back(i);
      }
      i++;
    }
    cout << ans << endl;
    for (auto& it : (tmp)) cout << it << " ";
    cout << endl;
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  func();
  return 0;
}
