ыыыы

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cmath>


int main() {
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    int n, k;
    std::cin >> n >> k;
    int min = 0, now = 0;
    std::string s;
    std::cin >> s;
    if (s.back() == 'C')
        s.pop_back();
    for (auto a : s) {
        if (a == 'A') {
            now++;
        } else if (a == 'C') {
            now--;
            min = std::min(now, min);
        }
    }
    if (min + k >= 0)
        std::cout << 0;
    else
        std::cout << -(min + k);
    return 0;
}