BiggestPrimeNum

#Solution:



def BiggestPrimeNumberSOE(num):
    prime = [True for i in range(num+1)]
# boolean array
    p = 2
    while (p * p <= num):

        # If prime[p] is not changed, then it is a prime
        if (prime[p] == True):

            # Updating all multiples of p
            for i in range(p * p, num+1, p):
                prime[i] = False
        p += 1

    # Print all prime numbers
    list = []
    for p in range(2, num+1):
        if prime[p]:
            list.append(p)
    print(max(list))


# ==
if __name__ == '__main__':
    num = int(input())

    BiggestPrimeNumberSOE(num)

# # Driver Program
# n = int(input())
# list = []
# for n in range(n+1):
#     if (isPrime(n)):
#         list.append(n)
#     else:
#         continue
# print(max(list))


#add variable where the primes are added in list? and then I search for the bigger number


# Description of the task
'''Biggest Prime Number
Description
Write a program that finds all prime numbers in the range [1 ... N]. Use the Sieve of Eratosthenes algorithm. The program should print the biggest prime number which is <= N.

Input
On the first line you will receive the number N
Output
Print the biggest prime number which is <= N
Constraints
2 <= N <= 10 000 000
Sample tests
Input	Output
13	13
126	113
26	23
'''



#Resources and tests

'''
def BiggestPrimeNumberSOE(num):
    prime = [True for i in range(num+1)]
# boolean array
    p = 2
    while (p * p <= num):

        # If prime[p] is not changed, then it is a prime
        if (prime[p] == True):

            # Updating all multiples of p
            for i in range(p * p, num+1, p):
                prime[i] = False
        p += 1

    # Print all prime numbers
    for p in range(2, num+1):
        if prime[p]:
            print(p)


# ==
if __name__ == '__main__':
    num = int(input())
    print(num)
    BiggestPrimeNumberSOE(num)'''



# def isPrime(n, i = 2):

#     # Base cases
#     if (n <= 2):
#         return True if(n == 2) else False
#     if (n % i == 0):
#         return False
#     if (i * i > n):
#         return True

#     # Check for next divisor
#     return isPrime(n, i + 1)


# # Driver Program
# n = int(input())
# list = []
# for n in range(n+1):
#     if (isPrime(n)):
#         list.append(n)
#     else:
#         continue
# print(max(list))