#include <bits/stdc++.h>
using namespace std;

struct uns_t {} uns;
template <typename Element, typename Head, typename ...Args>
auto vec(Element init, Head arg, Args ...args) {
    if constexpr (sizeof...(Args) == 0) return std::vector(arg, init);
    else return std::vector(arg, vec(init, args...));
}
template <typename Element, typename Head, typename ...Args>
auto vec(uns_t, Head arg, Args ...args) {
    return vec(Element(), arg, args...);
}

int main() {
    int n, k; cin >> n >> k;
    string s; cin >> s;

    auto dp = vec<bool>(false, n);

    int idx = n - 1;
    while (0 < idx) {
        if (s[idx - 1] == 'x') {
            idx -= 1;
            continue;
        }
        dp[idx] = true;
        idx -= k + 1;
    }

    for (int i = 1; i < n && i <= k; ++i) {
        if (dp[i]) {
            cout << i << endl;
            return 0;
        }
    }

    cout << 0 << endl;
}