import random

def isPrimeMillerRabin(n, k=3):
    if n <= 1:
        return False
    if n == 2 or n == 3:
        return True
    if n % 2 == 0:
        return False

    r, d = 0, n - 1
    while d % 2 == 0:
        r += 1
        d //= 2

    # Perform Miller-Rabin test k times
    for _ in range(k):
        a = random.randint(2, n - 2)
        x = pow(a, d, n)

        if x == 1 or x == n - 1:
            continue

        for _ in range(r - 1):
            x = pow(x, 2, n)
            if x == n - 1:
                break
        else:
            return False  

    return True  # Likely to be prime


N = float(input()) / 100
count = 0
i = 3  
spiral_size = 1

while True:
    for j in range(4):
        num = i**2 - (i - 1) * j
        if isPrimeMillerRabin(num):
            count += 1
            
    spiral_size += 4
    proportion = count / spiral_size

    if proportion < N:
        break

    i += 2  

print(i)