private int[] help(String s, int l) {
	        int res = 0, sign = 1;
	        int r = l;
	        while (r < s.length()) {
	            char ch = s.charAt(r);
	            if (ch == ' ')
	                r++;
	            else if (ch == '+') {
	                sign = 1;
	                r++;
	            } else if (ch == '-') {
	                sign = -1;
	                r++;
	            } else if (ch == '(') {
	                int[] subs = help(s, r+1);
	                int num = subs[0];
	                res += sign*num;
	                r = subs[1] + 1;
	            } else if (ch == ')')
	                break;
	            else {
	                int num = 0;
	                while (r < s.length() && Character.isDigit(s.charAt(r))) {
	                    num = num*10 + s.charAt(r) - '0';
	                    r++;
	                }
	                res += sign*num;
	            }
	        }
	        
	        return new int[]{res, r};
	    }