#include <iostream>
using namespace std;

int power(int a, int n) {
    int number = 1;

    while (n) {
        if (n & 1) {
            number *= a;
            n--;
        }
        else {
            a *= a;
            n >>= 1;
        }
    }

    return number;
}

int number(int *array, int size) {
    int length = size / sizeof(array[0]);
    int sum = array[0];

    for (int i = 1; i != length; i++)
        sum += array[i] * power(10, i);

    return sum;
}

int mul(int *a, int *b, int size_a, int size_b) {
    return number(a, size_a) * number(b, size_b);
}

int main() {
    int a[3] = {1, 2, 3};
    int b[3] = {4, 5, 6};

    cout << mul(a, b, sizeof(a), sizeof(b)) << endl;

    return 0;
}