# 255.255.255.0 24
# 255.255.0.0 16
# 255.0.0.0 8

def subnet_mask_to_cidr(subnet_mask):
    # Split the subnet mask into its octets
    octets = subnet_mask.split('.')
    
    # Convert each octet to binary and count the number of 1s
    binary_representation = ''.join(format(int(octet), '08b') for octet in octets)
    print(binary_representation)
    cidr = binary_representation.count('1')
    
    return cidr

# Example usage
subnet_mask = '255.255.255.240'
cidr = subnet_mask_to_cidr(subnet_mask)
print(f"The CIDR notation for subnet mask {subnet_mask} is /{cidr}")