This is a practice problem!
A prime number is an integer greater than 1 that is divisible only by itself and 1. Write a program that will read integers and print “yes” or “no” depending on whether or not each integer is prime.
The input to the program will be a series of integers, one per line. As a special case, if an integer is negative, the program should exit immediately without producing additional output.
Example input:
1 2 4 5 17 21 23 -1
Example output: (corresponding to the example input shown above):
no yes no yes yes no yes