Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -.

Example:
Given a = 1 and b = 2, return 3.

Credits:
Special thanks to @fujiaozhu for adding this problem and creating all test cases.

public class Solution {
    public int GetSum(int a, int b) {
		int sum = 0;
		while (b != 0) {
			sum = a ^ b;
			b = (a & b) << 1;
			a = sum;
		}
		return sum;
    }
}