luhn

#include <iostream>

using namespace std;

int main() {
    string card;
    int digit, sum = 0, alternate = 0;

    cin >> card;

    for (int i = card.length() - 1; i >= 0; i--) {
        digit = card[i] - '0'; //int cast convert digit to integer

        if (alternate == 1)
            digit = digit * 2;

        sum = sum + digit / 10;
        sum = sum + digit % 10;

        alternate = !alternate;
    }

    if (sum % 10 == 0) {
        if (card[0] == '4' && card.length() >=13 && card.length()<= 16) {
            cout << "Visa";
        }
        else if (card[0] == '5' && card[1]>='1' && card[1]<='5' && card.length() == 16) {
            cout << "Mastercard";
        }
        else if (card[0] == '3' && (card[1]=='4' || card[1]=='7') && card.length() == 15) {
            cout << "Amex";
        }
        else {
            cout << "Almost";
        }
    }
    else {
        cout << "Invalid";
    }
    return 0;
}