class Solution {

public String addStrings(String num1, String num2) {

String big = num2;

String small = num1;

if (num1.length() > num2.length()) {

big = num1;

small = num2;

}

StringBuilder answer = new StringBuilder("");

int small_i = small.length() - 1;

int big_i = big.length() - 1;

int carryOver = 0;

while (small_i >= 0) {

int mid = Integer.parseInt(String.valueOf(small.charAt(small_i))) + Integer.parseInt(String.valueOf(big.charAt(big_i))) + carryOver;

carryOver = mid/10;

mid = mid%10;

answer.append(String.valueOf(mid));

small_i--;

big_i--;

}

while (big_i >= 0) {

int mid = Integer.parseInt(String.valueOf(big.charAt(big_i))) + carryOver;

carryOver = mid/10;

mid = mid%10;

answer.append(String.valueOf(mid));

big_i--;

}

return carryOver > 0 ? String.valueOf(carryOver) + answer.reverse().toString() : answer.reverse().toString();

}

}