rollNum = input("Your roll number?")
if rollNum[0] == 'C':
    if rollNum[1] == 'S':
        print("Hi Bro!")
else:
    print("Excuse me?")

if rollNum[0] == 'C' and rollNum[1] == 'S':
    print("Hi Bro!")
else:
    print("Excuse me?")

if rollNum[0:2] == 'CS':
    print("Hi Bro!")
else:
    print("Excuse me?")


if (rollNum[0] == 'C' or rollNum[0] == 'c') and \
(rollNum[1] == 'S' or rollNum[1] == 's'):
    print("Hi Bro!")
else:
    print("Excuse me?")

if (rollNum[0] == 'C' and rollNum[1] == 'S') or (rollNum[0] == 'c' and rollNum[1] == 's'):
    print("Hi Bro!")
else:
    print("Excuse me?")


if rollNum[0:2].upper() == 'CS':
    print("Hi Bro!")
else:
    print("Excuse me?")

if not (rollNum[0:2].upper() == 'CS'):
    print("Excuse me?")
else:
    print("Hi Bro!")