Python-сообщество

 s = input()
x = len(s)
l1 = x - x // 2
print(s[l1:] + s[:l1])

 //

 s = '1234567'
h = sum(divmod(len(s), 2))
s[h:] + s[:h]

 from contextlib import ExitStack
  
with ExitStack() as stack:
    fin = stack.enter_context(open('input.txt', 'r', encoding='utf8'))
    fout = stack.enter_context(open('output.txt', 'w', encoding='utf8'))
    while True:
        s = fin.readline()[:-1]
        if not s:
            break
        x = len(s)
        l1 = x - x // 2
        print(s[l1:] + s[:l1], file=fout)

 with open('input.txt', 'w', encoding='utf8') as fout:
    print('123', file=fout)
    print('1234', file=fout)
    print('1', file=fout)
    print('12345', file=fout)
    print('123456', file=fout)

 with open('output.txt', 'r', encoding='utf8') as fin:
    print(fin.read())