public class Test {

    static String check(String input) {
        int counter = 0;
        for (int pos = 0; pos < input.length(); pos++) {
            char c = input.charAt(pos);
            if (c == '(') {
                counter++;
            }
            if (c == ')') {
                counter--;
            }
            if (counter == -1) {
                return "False";
            }
        }
        if (counter == 0) {
            return "True";
        } else {
            return "False";
        }
    }

    public static void main(String[] args) {
        System.out.println(check("()()")); // true
        System.out.println(check("(()())")); // true
        System.out.println(check(")("));   // false
        System.out.println(check("(()"));  // false
        System.out.println(check("()("));  // false
        System.out.println(check("((((")); // false
    }

}