import sys
import math
import bisect

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() import sys sys import math math import bisect bisect 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
import sys
import math
import bisect

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()
