def resolve():
    N, K = map(int, input().split())
    S = list(input())

    S[K - 1] = S[K - 1].lower()

    print(''.join(S))


resolve() def resolve():
    N, K = map(int, input().split())
    S = list(input())

    S[K - 1] = S[K - 1].lower()

    print(''.join(S)) resolve 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 resolve() resolve def resolve():
    N, K = map(int, input().split())
    S = list(input())

    S[K - 1] = S[K - 1].lower()

    print(''.join(S)) def resolve():
    N, K = map(int, input().split())
    S = list(input())

    S[K - 1] = S[K - 1].lower()

    print(''.join(S)) resolve
def resolve():
    N, K = map(int, input().split())
    S = list(input())

    S[K - 1] = S[K - 1].lower()

    print(''.join(S))


resolve()