n,k = map(int, input().split())
s = input()
ans = [s[:k-1],s[k-1].lower(),s[k:]]
print(''.join(ans))

 n,k = map(int, input().split()) n map(int, input().split()) map int input().split() ().split () input split k s = input() s input() input ans = [s[:k-1],s[k-1].lower(),s[k:]] ans [s[:k-1],s[k-1].lower(),s[k:]] 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 print(''.join(ans)) print ''.join(ans) ''.join '' join ans s = input() input() s n,k = map(int, input().split()) map(int, input().split()) n k = map(int, input().split()) map(int, input().split()) k ans = [s[:k-1],s[k-1].lower(),s[k:]] [s[:k-1],s[k-1].lower(),s[k:]] ans
n,k = map(int, input().split())
s = input()
ans = [s[:k-1],s[k-1].lower(),s[k:]]
print(''.join(ans))


