702 B | 702 chars
a,b= input().split()
a = int(a)
ans = ["","",""]
ans[a-1] = b[:]
if a == 1:
L = []
s= ""
for i in b:
if 'A' <= i <='Z':
L.append(s)
s = chr(ord(i)+32)
else:
s+=i
L.append(s)
ans[1] = "_".join(L)
ans[2] = chr(ord(b[0])-32) + b[1:]
elif a == 2:
L = b.split("_")
for i in L:
ans[2] += i[0].upper() + i[1:]
ans[0] = ans[2][0].lower() + ans[2][1:]
else:
ans[0] = b[0].lower() + b[1:]
L = []
s= ""
for i in ans[0]:
if 'A' <= i <='Z':
L.append(s)
s = chr(ord(i)+32)
else:
s+=i
L.append(s)
ans[1] = "_".join(L)
for i in ans:
print(i)