1.
# coding: utf-8
# Python 3.X
n = str(int(input('Число: ')))
print(n[3] + n[1:3] + n[0])
2.
# coding: utf-8
# Python 3.X
n = str(int(input('Число: ')))
print(n[0] + n[2:4])
3.
# coding: utf-8
# Python 3.X
n = str(int(input('Число: ')))
print(n[1:3])