Why can't I print a random number from 1 to a variable?

I was making a python program where you type in an input, and it finds a random number from 1 to that input. It won't work for me for whatever reason.

I tried using something like this

import random
a = input('pick a number: ')
print(random.randint(1, a))
input("Press enter to exit")

but it won't work for me, because as soon as it starts to print it, cmd prompt just closes. does anyone know how to fix this?