#include <stdio.h>
#define N 1000000


int main() {
    int n, k;
    char a[N];
    scanf("%d %d", &n, &k);
    scanf("%s", a);
    int i, f;
    int y = 0;
    int b[N];  //定义数组b用于计算ou，oku，okk....分别的数量
    for (i = 0; i < n; i++) {
        b[i] = 0;  //初始化b
    }
    for (i = 0; i < n; i++) {
        if (a[i] == 'O') {
            int j;
            int h = 0;
            f = 0;
            int count = 0;
            for (j = 1; i + j < n; j++) {
                if (a[i + j] == 'K') {
                    count = count + 1;
                    if (i + j == n - 1) {
                        f = 1;
                        break;
                    }
                }
                if (a[i + j] == 'O') {
                    f = 1;
                    break;
                }
                if (a[i + j] == 'U') {
                    h = 1;
                    break;
                }
            }
            if (f == 0 && h == 1) {
                b[count]++;
            }
        }
    }
    int q = 0, s = 0;
    int m = k;
    for (i = 0; i < n; i++) {
        k = k - i * b[i];
        if (k <= 0) {
            q = i;
            s = k + i * b[i];
            break;
        }
    }
    int count3 = 0;
    if (k >= 0) {
        for (i = 0; i < n; i++) {
            count3 += b[i];
        }
    }
    if (k < 0) {
        for (i = 0; i < q; i++) {
            count3 += b[i];
        }
        count3 = count3 + s / q;
    }
    printf("%d", count3);
}