def get_count(num):
    count = 0   # 自守数的个数
    for n in range(num+1):
        np = pow(n,2)
        length = len(str(n))
        if int(str(np)[-length:]) == n:  # 自守数的条件
            count += 1
    return count



while True:
    try:
        n = int(input())
        print(get_count(n))
    except:
        break