def is_prime(n):
# We know 1 is not a prime number
if n == 1:
return False
i = 2
while i*i <= n:
if n % i == 0:
return False
i += 1
return True
if name == 'main':
inp = open("input.txt", "r")
out = open("output.txt", "w")
prev = 1
primeCount = 0
while True:
line = inp.readline()
if not line.isnumeric():
continue
prev = int(line.strip())
if prev == 0:
break
if prev < 0:
continue
if is_prime(prev):
primeCount += 1
out.write(str(primeCount))