Sum of two number in array

#include<iostream>
using namespace std;

int main(){
    int t; cin >> t;
    while(t--){
        int n, m; cin >> n >> m;
        unsigned long long int first_num = 0, second_num = 0, i, temp;
        //  Taking input of First array
        for(i = 0; i < n; i++){
            cin >> temp;
            first_num *= 10;
            first_num += temp;
        }
        //  Taking input of Second array
        for(i = 0; i < m; i++){
            cin >> temp;
            second_num *= 10;
            second_num += temp;
        }
        //  Adding them together
        temp = first_num + second_num;

        //  Making the result array
        int index = 0;
        int k = temp;
        while(k){
            k /= 10;
            index++;
        }
        int result[index];
        //k = index;
        for(i = index-1; i > -1; i--){
            result[i] = temp % 10;
            temp /= 10;
        }
        //  Showing the result
        for(i = 0; i < index; i++) cout << result[i] << ' ';
        cout << endl;
    }
}