#include <stdio.h>

int main () {
  int n = 0;
  char s[200001] = "";
  
  int res = 0;
  
  long long ans = 0LL;
  
  long long cnt = 0LL;
  long long sum = 0LL;
  
  res = scanf("%d", &n);
  res = scanf("%s", s);
  for (int i = 0; i < n; i++) {
    if (s[i] != 'A') {
      sum += 1LL;
    }
  }
  
  for (int i = 0; i < n; i++) {
    if (s[i] == 'A') {
      cnt += 1LL;
    } else if (s[i] == 'C') {
      ans += cnt;
      sum -= 1LL;
    } else if (sum > cnt) {
      cnt += 1LL;
      sum -= 1LL;
    } else {
      ans += cnt;
      sum -= 1LL;
    }
  }
  
  printf("%lld\n", ans);
  return 0;
}