import java.util.*;

public class ParenBalancing5 {

    public static void main (String[] argv)
    {
        // Test 1.
	String s = "((()))";
	int index = checkParens (s);
        if (index >= 0) {
            System.out.println ("Unbalanced: mismatch at position " + index + " in string " + s);
        }
        else {
            System.out.println ("String " + s + " has balanced parens");
        }

        // Test 2.
	s = "((())";
	index = checkParens (s);
        if (index >= 0) {
            System.out.println ("Unbalanced: mismatch at position " + index + " in string " + s);
        }
        else {
            System.out.println ("String " + s + " has balanced parens");
        }

        // Test 3.
	s = "())))";
	index = checkParens (s);
        if (index >= 0) {
            System.out.println ("Unbalanced: mismatch at position " + index + " in string " + s);
        }
        else {
            System.out.println ("String " + s + " has balanced parens");
        }

    }


    static int checkParens (String inputStr)
    {
	char[] letters = inputStr.toCharArray();
	Stack<Character> stack = new Stack<Character> ();

	for (int i=0; i<letters.length; i++) {
	    if (letters[i] == '(') {
		stack.push (letters[i]);
	    }
	    else if (letters[i] == ')') {
		// Look for a match on the stack.
		char ch = ')';
		if (! stack.isEmpty() ) {
		    ch = stack.pop ();
		}
		if (ch != '(') {
                    // Return the position where the mismatch occured.
		    return i;
		}
	    }
	}
	
        // If we've reached here, either there's no mismatch, or
        // the mismatch is because of unmatched parens still on the stack.
	if ( ! stack.isEmpty() )  {
	    return letters.length;
	}
	else {
            return -1;
        }
    }

}