#!/usr/bin/env python3
import sys
try:
    from typing import List
except ImportError:
    pass


def solve(N: int, K: int, S: str):
    print(S[:K - 1] + S[K - 1].lower() + S[K:])


def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  # type: int
    K = int(next(tokens))  # type: int
    S = next(tokens)  # type: str
    solve(N, K, S)


if __name__ == '__main__':
    main() import sys sys try:
    from typing import List
except ImportError:
    pass except ImportError:
    pass from typing import List def solve(N: int, K: int, S: str):
    print(S[:K - 1] + S[K - 1].lower() + S[K:]) solve print(S[:K - 1] + S[K - 1].lower() + S[K:]) print S[:K - 1] + S[K - 1].lower() + S[K:] S[:K - 1] + S[K - 1].lower() S[:K - 1] S :K - 1 K - 1 K 1 S[K - 1].lower() [K - 1].lower [K - 1] S K - 1 K 1 lower S[K:] S K: K N: int N K: int K S: str S def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  # type: int
    K = int(next(tokens))  # type: int
    S = next(tokens)  # type: str
    solve(N, K, S) main def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
     iterate_tokens for line in sys.stdin:
            for word in line.split():
                yield word
     line sys.stdin sys stdin for word in line.split():
                yield word
     word line.split() line.split line split yield word word tokens = iterate_tokens() tokens iterate_tokens() iterate_tokens N = int(next(tokens)) N int(next(tokens)) int next(tokens) next tokens K = int(next(tokens)) K int(next(tokens)) int next(tokens) next tokens S = next(tokens) S next(tokens) next tokens solve(N, K, S) solve N K S if __name__ == '__main__':
    main() __name__ == '__main__' __name__ '__main__' main() main def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  # type: int
    K = int(next(tokens))  # type: int
    S = next(tokens)  # type: str
    solve(N, K, S) def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  # type: int
    K = int(next(tokens))  # type: int
    S = next(tokens)  # type: str
    solve(N, K, S) main def solve(N: int, K: int, S: str):
    print(S[:K - 1] + S[K - 1].lower() + S[K:]) def solve(N: int, K: int, S: str):
    print(S[:K - 1] + S[K - 1].lower() + S[K:]) solve
#!/usr/bin/env python3
import sys
try:
    from typing import List
except ImportError:
    pass


def solve(N: int, K: int, S: str):
    print(S[:K - 1] + S[K - 1].lower() + S[K:])


def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  # type: int
    K = int(next(tokens))  # type: int
    S = next(tokens)  # type: str
    solve(N, K, S)


if __name__ == '__main__':
    main()
