def main():
    N, K = map(int, input().split())
    S = list(input())
    S[K-1] = S[K-1].lower()
    print("".join(S))


if __name__ == "__main__":
    main() def main():
    N, K = map(int, input().split())
    S = list(input())
    S[K-1] = S[K-1].lower()
    print("".join(S)) main N, K = map(int, input().split()) N map(int, input().split()) map int input().split() ().split () input split K S = list(input()) S list(input()) list input() input S[K-1] = S[K-1].lower() S[K-1] S K-1 K 1 S[K-1].lower() [K-1].lower [K-1] S K-1 K 1 lower print("".join(S)) print "".join(S) "".join "" join S if __name__ == "__main__":
    main() __name__ == "__main__" __name__ "__main__" main() main def main():
    N, K = map(int, input().split())
    S = list(input())
    S[K-1] = S[K-1].lower()
    print("".join(S)) def main():
    N, K = map(int, input().split())
    S = list(input())
    S[K-1] = S[K-1].lower()
    print("".join(S)) main
def main():
    N, K = map(int, input().split())
    S = list(input())
    S[K-1] = S[K-1].lower()
    print("".join(S))


if __name__ == "__main__":
    main()