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