Card Number - Bank Identification

#include <iostream>
using namespace std;

int size_str(char * str) {
    int size = 0;
    while (str[size] != 0) {
        size++;
    }

    return size;
}

int return_int_char_hz(char * num, int a, int b) {
    int chislo = 0;
    for (int i = 0; b >= a + i; i++) {
        chislo = chislo * 10 + (num[a + i] - 48);
    }

    return chislo;
}


int main() {
    char * card_num;
    char * next_card_num;
    int size_card_num;
    enter_card_number: ;
    card_num = new char[16];
    cout << "Enter card number: ";
    cin >> card_num;

    size_card_num = size_str(card_num);
    while(size_str(card_num) < 16) {
        next_card_num = new char[4];
        cin >> next_card_num;

        for(int i = 0; size_str(next_card_num) > i; i++) {
            card_num[size_card_num + i] = next_card_num[i];
        }

        size_card_num += size_str(next_card_num);
        delete next_card_num;
    }

    if (size_card_num > 16) {
        cout << "Invalid number card. Enter card number again.\n";
        delete card_num;
        goto enter_card_number;
    }

    for(int i = 0; i < 16; i++) {
        if (card_num[i] < 48 || 57 < card_num[i]) {
            cout << "Invalid number card. Enter card number again.\n";
            delete card_num;
            goto enter_card_number;
        }
    }

    // Payment system
    switch (card_num[0]) {
        case '2':
            cout << "Payment system: MIR" << endl;
            break;
        case '3':
            cout << "Payment system: American Express/Maestro/JCB International" << endl;
            break;
        case '4':
            cout << "Payment system: VISA" << endl;
            break;
        case '5':
            cout << "Payment system: MasterCard" << endl;
            break;
        case '6':
            cout << "Payment system: China UnionPay" << endl;
            break;
        case '7':
            cout << "Payment system: UEC" << endl;
            break;
        default:
            cout << "Payment system: undefined" << endl;
            break;
    }

    int num1 = return_int_char_hz(card_num, 1, 4);
    int num2 = return_int_char_hz(card_num, 1, 5);

    int ** banks = new int * [7];
    banks[0] = new int [7] {15428, 5841, 77964, 21178, 48601, 48673, 76371}; // alfabank
    banks[1] = new int [5] {27229, 47520, 27883, 6223, 2006}; // VTB24
    banks[2] = new int [6] {16792, 65204, 25744, 48265, 54373, 65203}; // MDM
    banks[3] = new int [4] {5870, 34146, 32301, 44573}; // otkritie
    banks[4] = new int [6] {47817, 47818, 76206, 76208, 54759, 20373}; // promsvyazbank
    banks[5] = new int [12] {4693, 3900, 7758, 27601, 27631, 27644, 27683, 27901, 4696, 4692, 4691, 2022}; // sberbank
    banks[6] = new int [11] {11900, 24553, 24554, 56515, 90986, 94343, 29047, 57808, 57809, 76642, 31318}; // trast

    int counts[7] = {7, 5, 6, 4, 6, 12, 11};
    int name_bank = -1;

    for (int i = 0; 7 > i; i++) {
        int count = counts[i];
        for (int j = 0; j < count; j++) {
            if (banks[i][j] == num1 || banks[i][j] == num2) {
                name_bank = i;
            }
        }
    }

    switch (name_bank) {
        case 0:
            cout << "Bank: Alfabank" << endl;
            break;
        case 1:
            cout << "Bank: VTB24" << endl;
            break;
        case 2:
            cout << "Bank: MDM" << endl;
            break;
        case 3:
            cout << "Bank: Otrkitie" << endl;
            break;
        case 4:
            cout << "Bank: Promsvyazbank" << endl;
            break;
        case 5:
            cout << "Bank: Sberbank" << endl;
            break;
        case 6:
            cout << "Bank: Trast" << endl;
            break;
        default:
            cout << "Bank: undefined" << endl;
            break;
    }

    return 0;
}