while True:
try:
num = int(input())
count = 0
if num > 4:
for i in range(2,num): #用num//2可以减少回圈次数
if num % i == 0:
count += 1
if count == 1:
print('no')
break
if count == 0:
print('yes')
elif num == 2&nbs***bsp;num == 3:
print('yes')
else:
print('no')
except:
break isPrime = lambda n:'yes' if not any([bool(n % i == 0) for i in xrange(2, int(n ** 0.5) + 1)]) else 'no'
try:
while 1:
n = input()
print 'no' if n <= 1 else isPrime(n)
except:
pass