n,k=map(int,input().split())
s=input()
count=0
result=''
for i in s:
    count+=1
    if count==k:
        S=i.lower()
        result+=S
    else:
        result+=i
print(result) n,k=map(int,input().split()) n map(int,input().split()) map int input().split() ().split () input split k s=input() s input() input count=0 count 0 result='' result '' for i in s:
    count+=1
    if count==k:
        S=i.lower()
        result+=S
    else:
        result+=i i s count+=1 count 1 if count==k:
        S=i.lower()
        result+=S
    else:
        result+=i count==k count k S=i.lower() S i.lower() i.lower i lower result+=S result S result+=i result i print(result) print result k=map(int,input().split()) map(int,input().split()) k count=0 0 count s=input() input() s n,k=map(int,input().split()) map(int,input().split()) n result+=S S result count+=1 1 count result+=i i result result='' '' result S=i.lower() i.lower() S
n,k=map(int,input().split())
s=input()
count=0
result=''
for i in s:
    count+=1
    if count==k:
        S=i.lower()
        result+=S
    else:
        result+=i
print(result)