#define _CRT_SECURE_NO_WARNINGS
#define _SILENCE_CXX17_C_HEADER_DEPRECATION_WARNING
#include <bits/stdc++.h>
using namespace std;
const int N = 3e5 + 50;
char s[N];
int main()
{
    int n;
    scanf("%d%s", &n, &s);
    for (int i = 1; i < n; i++)
    {
        if (s[i - 1] > s[i])
        {
            puts("YES");
            printf("%d %d", i, i + 1);
            exit(0);
        }
    }
    puts("NO");
    return 0;
}