mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    N, K = map(int, input().split())
    S = input().rstrip('\n')

    i = N-1
    while i > 0:
        if S[i-1] == "x":
            i -= 1
        else:
            break
    flg = 1
    while i > 0:
        if flg == 1:
            i -= K+1
            flg = 0
        else:
            if S[i-1] == "o":
                flg = 1
            else:
                i -= 1
    if i == 0:
        print(i)
    else:
        print(i + K + 1)


if __name__ == '__main__':
    main()