karatsuba

#include<iostream>
using namespace std;

int number_of_digits(long int number);// count number of digits
int separ_l(long int num);
int separ_r(long int num);
long int karatsuba_method(long int num1, long int num2);
int main() {
    long int num1, num2;
    cin >> num1 >> num2;
    //cout << karatsuba_method(num1, num2);
    //cout << separ_l(num1) << " " << separ_r(num1) << endl;
    //cout << separ_l(num2) << " " << separ_r(num2) << endl;
    //cout << number_of_digits(num1) << " " << number_of_digits(num2) << endl;
    cout << karatsuba_method(num1, num2);
    system("pause");
    return 0;
}
int number_of_digits(long int number) {
    int amount = 0;
    if (number > 1) amount = amount + number_of_digits(number / 10);
    amount++;
        return amount;
}
long int karatsuba_method(long int num1, long int num2) {
    long int  ANS;
    //num1_l = separ_l(num1);
    //num1_r = separ_r(num1);
    //num2_l = separ_l(num2);
    //num2_r = separ_r(num2);

    if (number_of_digits(separ_l(num1)) > 2)// break your brain
        ANS = (int) pow(10, number_of_digits(num1)) * karatsuba_method(separ_l(num1), separ_l(num2))
        + (int) (pow(10, number_of_digits(num1) / 2)) *
        karatsuba_method(separ_l(num1) + separ_r(num1), separ_l(num2) + separ_r(num2)) -
        karatsuba_method(separ_l(num1), separ_l(num2));
    else
        ANS = (int) pow(10, number_of_digits(num1)) * separ_l(num1)* separ_l(num2) +
        (int) (pow(10, number_of_digits(num1) / 2)) * (separ_l(num1) + separ_r(num1))*
        (separ_l(num2) + separ_r(num2)) - (separ_l(num1)*separ_l(num2));
    return ANS;
}
int separ_l(long int num) {// separates left part of number (lp is greater than half)
    return num / (long int)(powl(10, number_of_digits(num) / 2));
}
int separ_r(long int num) {// separates right part of number (rp is less than half)

    return num % (long int)(pow(10, number_of_digits(num) / 2));
}