class StackObject {
    char cr;
    int    loc;
    public StackObject(char c, int l) {
	cr = c;
        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(char a, char 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 []) {
	char [] str = {'(', '[', ']', '[', ']',']'}; 
        //string to be processed
        StackObject ObjectOnTop;
        int i =  0; // to iterate through str
        boolean done = false;
        //variable to indicate mismatch in the middle of processing str
        MyStack sta = new MyStack();
        while( (i < str.length) && ! done) {

	    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) {
		    done = true;
                    System.out.println("The character " + str[i] + " at position" + i + "has no match");
		}
                else if (! Auxiliaries.matches(ObjectOnTop.cr, str[i]) ) {
                    done = true;
		System.out.println("The " + str[i] + " at position " + i + " does not match the " + ObjectOnTop.cr + " at position " + ObjectOnTop.loc);
		}
	    }
            else {System.out.println("invalid character at position" + i);
		  done = true;
            }
            // Only used if str contains something other than paranths 

	
		i++;
	}

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