[4948] 베르트랑 공준

primeNumber = []
for i in range(2,123456*2+1):
    count = 0
    for j in range(2, int(i**0.5)+1):
        if i%j ==0:
            count += 1
            break
    if count ==0:
        primeNumber.append(i)
while True:
    n = int(input())
    result = 0
    if n ==0:
        break
    for i in primeNumber:
        if n <i <= 2*n:
            result +=1
    print(result)