# x = 'abcd'
# for i in x:
#     print(i)
#     x.upper()

# x = 'abcd'
# for i in x:
#     print(i.upper())

# x = 'abcd'
# for i in range(x):
#     print(i)

# x = 'abcd'
# for i in range(len(x)):
#     print(i)

# x = 'abcd'
# for i in range(len(x)):
#     print(i.upper())

# x = 'abcd'
# for i in range(len(x)):
#     i.upper()
# print (x)

# x = 'abcd'
# for i in range(len(x)):
#     x[i].upper()
# print (x)

# x = 'abcd'
# for i in range(len(x)):
#     i[x].upper()
# print (x)

# x = 'abcd'
# for i in range(len(x)):
#     x = 'a'
#     print(x)

x = 'abcd'
for i in range(len(x)):
    print(x)
    x = 'a'