// test.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <vector>
using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{

	int digits;
	cout<<"How many digits? ";
	cin>>digits;
	vector<int>arr;
	int sum = 0;
	cout<<"Enter credit card number ";
	for(int i=0; i<digits; i++)
	{
		int d;
		cin>>d;
		arr.push_back(d);
	}

		
	if(digits % 2 == 0)//even
	{
	for(int i=0; i<digits; i++)
		{
			if(arr[i] % 2 != 0)//odd
			{
				arr[i] *= 2;
				if(arr[i] > 9)
				{
					arr[i] -= 9;
				}
            }
		}
	}

	else //odd
	{
		for(int i=0; i<digits; i++)
		{
			if(arr[i] % 2 == 0)//even
			{
				arr[i] *= 2;
				if(arr[i] > 9)
				{
					arr[i] -= 9;
				}
            }
		}
     }

	for(int j=0; j<digits; j++)
	{
		sum += arr[j];

	}

	if(sum % 10 == 0)//valid
		cout<<"Valid Card" <<endl;
	else
		cout<<"Not Valid" <<endl;
	
	system("pause");
	
	
	return 0;
}