#include <iostream>
using namespace std;
const int MAX_SIZE = 100;
struct magacin {
    int a[MAX_SIZE];
    int at;

    void init() {
        at = -1;
    }

    bool isEmpty() {
        if(at == -1) {
            return true;
        }
        else {
            return false;
        }
    }

    bool isFull() {
        if(at == MAX_SIZE - 1) {
            return true;
        }
        else {
            return false;
        }
    }


    void push(int x) {
        if(isFull()) {
            cout << "Stack overflow" << endl;
            exit(-1);
        }
        at++;
        a[at] = x;
    }

    int peek() {
        if(isEmpty()) {
            cout << "empty stack" << endl;
            exit(-1);
        }

        return a[at];
    }

    int pop() {
        int front = peek();

        at--;
        return front;
    }



};

void func(magacin &m)
{
    magacin m2, m3;

    m2.init();
    m3.init();

    while(m.isEmpty() == false) {
        int p = m.pop();

        m2.push(p);
        m3.push(p);
    }

    while(m2.isEmpty() == false) {
        int p = m2.pop();
        m.push(p);
    }

    while(m.isEmpty() == false) {
        int p1 = m.pop();
        int p2 = m3.pop();

        int sum = p1 + p2;
        if(sum > 9) {
            sum = 9;
        }
        cout << sum;
    }

    cout << endl;




}
int main()
{
    magacin s;
    int no, element, c;
    s.init();
    cout << "Vnesete koj broj da se proveri:";
    cin >> no;
    while(no != 0) {
    element = no%10;
    no /= 10;
        s.push(element);
    }
    func(s);
    return 0;
}