N, K = map(int, input().split())
S = input()
 
if S[K-1] == 'A': rep = 'a'
elif S[K-1] == 'B': rep = 'b'
else: rep = 'c'

# (K-1)文字目まで + K文字目 + K+1文字目から
print(S[:K-1] + rep + S[K:]) N, K = map(int, input().split()) N map(int, input().split()) map int input().split() ().split () input split K S = input() S input() input if S[K-1] == 'A': rep = 'a'
elif S[K-1] == 'B': rep = 'b'
else: rep = 'c'

# (K-1)文字目まで + K文字目 + K+1文字目から S[K-1] == 'A' S[K-1] S K-1 K 1 'A' elif S[K-1] == 'B': rep = 'b' S[K-1] == 'B' S[K-1] S K-1 K 1 'B' print(S[:K-1] + rep + S[K:]) print S[:K-1] + rep + S[K:] S[:K-1] + rep S[:K-1] S :K-1 K-1 K 1 rep S[K:] S K: K S = input() input() S K = map(int, input().split()) map(int, input().split()) K N, K = map(int, input().split()) map(int, input().split()) N
N, K = map(int, input().split())
S = input()
 
if S[K-1] == 'A': rep = 'a'
elif S[K-1] == 'B': rep = 'b'
else: rep = 'c'

# (K-1)文字目まで + K文字目 + K+1文字目から
print(S[:K-1] + rep + S[K:])