N, K = map(int, input().split())
S = str(input())

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

if S[K-1] == "A":
  print(S[:K-1]+"a"+S[K:])
elif S[K-1] == "B":
  print(S[:K-1]+"b"+S[K:])
else:
  print(S[:K-1]+"c"+S[K:])