#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  string s;
  cin >> n >> s;
  for (int i = 1; i < int(s.size()); ++i) {
    if (s[i] < s[i - 1]) {
      cout << "YES" << endl;
      cout << i << " " << i + 1 << endl;
      return 0;
    }
  }
  cout << "NO" << endl;
  return 0;
}
