public String sumTask(String a, String b) {
		int add = 0;
		StringBuilder res = new StringBuilder();
		int m = a.length();
		int n = b.length();
		if (m < n) {
			String c = a;
			int p = m;
			a = b;
			b = c;
			m = n;
			n = p;
		}
		m--;
		n--;
		while (m >= 0) {
			int tmp = (int) (a.charAt(m) - '0') + add;
			add = 0;
			if (n >= 0)
				tmp += (int) (b.charAt(n) - '0');
			if (tmp > 9) {
				add++;
				tmp -= 10;
			}
			res.append((char) (tmp + '0'));
			m--;
			n--;
		}
		if (add > 0) {
			res.append('1');
		}
		return res.reverse().toString();
	}