class StackObject {
    String str;
    int    loc;
    public StackObject(String s, int l) {
	str = s;
        loc = l;
    }
}


class ListEl {
    Object obj;
    ListEl next;
    public ListEl(Object o) {
        obj = o;
        next = null;
    }
}

class MyStack {
    ListEl start;
    public MyStack() {
	start = null;
    }

    public void push (Object o) {
	ListEl newEl = new ListEl(o);
        newEl.next = start;
        start = newEl;
    }

    public Object pop () {
	if (start == null) {return null;}
        else {
            ListEl temp = start;
	    start = temp.next;
            temp.next = null;
            return temp.obj;
	}
    }
}

class Auxiliaries {
    public static boolean matches(String a, String b) {
	boolean ans = false;
        if ((a == "(") && (b == ")")) ans = true;
        if ((a == "[") && (b == "]")) ans = true;
        return ans;
    }
}

public class ParanthList {
    public static void main (String argv []) {
	String [] str = {"[","(", "[", "]", ")", "[", ")"}; 
        //string to be processed
        StackObject ObjectOnTop;
        int i =  0; // to iterate through str
        boolean notDone = true;
        //variable to indicate mismatch in the middle of processing str
        MyStack sta = new MyStack();
        while( (i < str.length) && notDone) {

	    if ( (str[i] == "(") || (str[i] == "[")) {
		sta.push(new StackObject(str[i],i));
	    }
            // push onto stack for open paranths
            else if( (str[i] == ")") || (str[i] == "]") ) {
                ObjectOnTop =  (StackObject) sta.pop();
                // pop otherwise, and process as below
                if (ObjectOnTop == null) {
		    notDone = false;
                    System.out.println("The character " + str[i] + " at position" + i + "has no match");
		}
                else if (! Auxiliaries.matches(ObjectOnTop.str, str[i]) ) {
                    notDone = false;
		System.out.println("The " + str[i] + " at position " + i + " does not match the " + ObjectOnTop.str + " at position " + ObjectOnTop.loc);
		}
	    }
            else {System.out.println("invalid character at position" + i);}
            // Only used if str contains something other than paranths 

	
		i++;
	}

        if ((sta.pop() != null) && notDone ) 
             System.out.println("Paranths need to be closed");
        
    }
}