Letters Combination - Java Basics Loops

import java.util.Scanner;

public class FOX {
    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

      char firstChar = input.nextLine().charAt(0);
      char secondChar = input.nextLine().charAt(0);
      char thurdChar = input.nextLine().charAt(0);
      int counter = 0;

        for (char i = firstChar; i <= secondChar ; i++) {
            for (char j = firstChar; j <= secondChar; j++) {
                for (char k = firstChar; k <= secondChar; k++) {
                    if (!(i == thurdChar || j == thurdChar || k == thurdChar)) {
                        counter++;
                        System.out.printf("%s%s%s ", i, j, k);
                    }
                }
            }
        }
        System.out.println(counter);
    }
}