#N = int(input())
#S = str(input())
#A, B = map(int, input().split())
#C = list(map(int, input().split()))

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

d = ["A", "B", "C"]
e = ["a", "b", "c"]

for i in range(N):
  if i == K - 1:
    inde = d.index(S[i])    
    print(e[inde], end = "")
  else:
    print(S[i], end = "") 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 d = ["A", "B", "C"] d ["A", "B", "C"] "A" "B" "C" e = ["a", "b", "c"] e ["a", "b", "c"] "a" "b" "c" for i in range(N):
  if i == K - 1:
    inde = d.index(S[i])    
    print(e[inde], end = "")
  else:
    print(S[i], end = "") i range(N) range N if i == K - 1:
    inde = d.index(S[i])    
    print(e[inde], end = "")
  else:
    print(S[i], end = "") i == K - 1 i K - 1 K 1 inde = d.index(S[i]) inde d.index(S[i]) d.index d index S[i] S i print(e[inde], end = "") print e[inde] e inde end = "" end "" print(S[i], end = "") print S[i] S i end = "" end "" K = map(int, input().split()) map(int, input().split()) K S = str(input()) str(input()) S e = ["a", "b", "c"] ["a", "b", "c"] e d = ["A", "B", "C"] ["A", "B", "C"] d inde = d.index(S[i]) d.index(S[i]) inde N, K = map(int, input().split()) map(int, input().split()) N
#N = int(input())
#S = str(input())
#A, B = map(int, input().split())
#C = list(map(int, input().split()))

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

d = ["A", "B", "C"]
e = ["a", "b", "c"]

for i in range(N):
  if i == K - 1:
    inde = d.index(S[i])    
    print(e[inde], end = "")
  else:
    print(S[i], end = "")
