Hang Nguyen sylviahangnguyen

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	#include <math.h> // library for pow()
	#include <cs50.h> // library for get_long()
	#include <stdio.h> // library for almost all C functions

	int countDigits(long card); // initialise the function to count the number of digits before the main function
	int sumDigits(long card, int len, unsigned long long int power); // initialise the function to check the Luhn sum

	int main(void)
	{
	// PROMPT THE CARD NUMBER (INPUT)

	Initialise the 1stsub function to count the number of digits before the main function
	Initialise the 2nd sub function to check the Luhn sum

	Main funtion
	// PROMPT THE CARD NUMBER (INPUT)
	Initialise the type of card (from 13 to 16 digits)
	Get the card number from user
	Avoid the negative long and 0

	// GET THE DIGIT COUNT TO CHECK FOR THE CARD'S LENGTH => CARD'S TYPE