if name == 'main':
inp = open("input.txt", "r")
out = open("output.txt", "w")
prev = 1.0
primeCount = 0
while True:
line = inp.readline()
if prev == 0.0:
break
prev = float(line.strip())
if prev == 2.0 or prev == 3.0:
primeCount += 1
elif prev > 3.0:
isPrime = False
i = 2.0
while i * i <= prev:
if prev % i == 0.0:
isPrime = False
break
isPrime = True
i += 1.0
if isPrime:
primeCount += 1
out.write(str(primeCount))