#include <iostream>
#include <cstdlib>
#include <string>
#include <cassert>
#include <cctype>

using namespace std;

const int BIGINT_SIZE(100);
typedef unsigned int BIGINT[BIGINT_SIZE];

istream & operator >>(istream & is,  BIGINT & b)
{
    string s;
    is >> s;

    for (int i = 0; i < BIGINT_SIZE; ++i)
        b[i] = 0;

    for (int i = 0; i < s.length(); ++i)
    {
        assert(isdigit(s[i]));
        b[s.length() - 1 - i] = s[i] - '0';
    }

    return is;

}


ostream & operator <<(ostream & os, const BIGINT b)
{
    int i;

    for (i = BIGINT_SIZE - 1; i >= 0 && b[i] == 0; --i)
        ;

    if (i < 0) // number zero
        os << "0";
    else
        while (i >= 0)
            os << b[i--];


    return os;
}

void add(const BIGINT x, const BIGINT y, BIGINT answer)
{
    for (int i = 0; i < BIGINT_SIZE; ++i)
        answer[i] = 0;


    unsigned int carry(0);
    for (int i = 0; i < BIGINT_SIZE; ++i)
    {
        int sum = x[i] + y[i] + carry;
        answer[i] = sum % 10;
        carry = sum / 10;
    }


}


int main()
{

    BIGINT b, c, a;


    cout << "Enter two bigint: ";
    cin >> b >> c;
    cout << "Read bigint: "  << b << ", " << c << endl;

    add(b, c, a);

    cout << "Addition: " << a << endl;

}