import java.util.Scanner;
import java.util.Stack;

public class DelimiterChecker {
    
    public static final int NO_ERROR = 0;
    public static final int MATCHING_ERROR = 1;
    public static final int MISSING_RIGHT_DELIMITER_ERROR = 2;
    public static final int MISSING_LEFT_DELIMITER_ERROR = 3;
    
    public boolean isValid(String inputStr) {
          
      Stack<Character> stack = new Stack<Character>(); 
    
      //get chars in turn...
      for(int j=0; j<inputStr.length(); j++) {
         char ch = inputStr.charAt(j); // get char
         switch(ch) {
            case '{': // opening symbols
            case '[':
            case '(':
                       stack.push(ch); // push them
                       break;
            case '}': // closing symbols
            case ']':
            case ')':
                       if ( !stack.isEmpty() ) {
                           char chx = stack.pop(); // pop and check
                           if ( (ch=='}' && chx!='{') ||
                                (ch==']' && chx!='[') ||
                                (ch==')' && chx!='(')    ) {                           
                              printError(inputStr, j, MATCHING_ERROR);
                              return false;
                           }
                       }
                       else { // prematurely empty 
                           printError(inputStr, j, MISSING_LEFT_DELIMITER_ERROR);
                           return false;
                       }
                       break;
            default: // no action on other characters
                       break;
         } // end switch
      } // end for
      
    // at this point, all characters have been processed
    if ( !stack.isEmpty() ) {
        printError(inputStr, inputStr.length(), MISSING_RIGHT_DELIMITER_ERROR);
        return false;
    }
    
    printError(inputStr, 0, NO_ERROR);
    return true;
    
  } // end isValid()
    
  private void printError(String inputStr, int posOfError, int typeOfError) {
      
      if (typeOfError != NO_ERROR) {
          System.out.println(inputStr);
          
          for (int i=0; i < posOfError; i++) {
              System.out.print(" ");
          }
          System.out.println("^");  // a visual marker of where the error has occurred 
      }

      switch (typeOfError) {
          case MATCHING_ERROR                : 
              System.out.println("Paired delimeters do not match"); break;
          case MISSING_RIGHT_DELIMITER_ERROR : 
              System.out.println("Missing right delimiter"); break;
          case MISSING_LEFT_DELIMITER_ERROR  : 
              System.out.println("Missing left delimiter"); break;
      }
  }
    
  public static void main(String[] args) {
     DelimiterChecker dc = new DelimiterChecker();
     System.out.println("Enter an expression to check..");
     Scanner scanner = new Scanner(System.in);
     String s = scanner.nextLine();
     scanner.close();
     System.out.println();
     System.out.println( (!dc.isValid(s) ? "An error was found" : "No errors were found"));
  }

}