N,K=map(int,input().split())
S=input()
a=S[0:K-1]
b=S[K:]
c=S[K-1]
c=c.lower()
print(a+c+b) N,K=map(int,input().split()) N map(int,input().split()) map int input().split() ().split () input split K S=input() S input() input a=S[0:K-1] a S[0:K-1] S 0:K-1 0 K-1 K 1 b=S[K:] b S[K:] S K: K c=S[K-1] c S[K-1] S K-1 K 1 c=c.lower() c c.lower() c.lower c lower print(a+c+b) print a+c+b a+c a c b a=S[0:K-1] S[0:K-1] a b=S[K:] S[K:] b K=map(int,input().split()) map(int,input().split()) K c=c.lower() c.lower() c N,K=map(int,input().split()) map(int,input().split()) N c=S[K-1] S[K-1] c S=input() input() S
N,K=map(int,input().split())
S=input()
a=S[0:K-1]
b=S[K:]
c=S[K-1]
c=c.lower()
print(a+c+b)