#include <stdio.h>

const int min(const int a, const int b);
const int min(const int a, const int b) { return (b < a) ? b : a; }

int main() {
    int n_friends, mood;
    char friends [200001];
    scanf("%d %d\n%200000s", &n_friends, &mood, friends);

    int min_mood = mood;

    for (int i = 0; i < n_friends - 1; i++) {
        if (friends[i] == 'A') { mood++; min_mood = min(min_mood, mood); }
        else if (friends[i] == 'C') { mood--; min_mood = min(min_mood, mood); }
    }

    printf("%d", -min(0, min_mood));
    return 0;
}