package com.company;
import java.util.Scanner;
public class Six_sixtyThree {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("Input User ID: ");
        String ID = input.nextLine();

     for(int i =0; i < 2; i++ )
     {
         int target = Integer.parseInt(ID.substring())
         target = ID.intAt(i);
         ID = ID.replaceFirst(target,"_");
     }
    }
    }
//    String s = Integer.toString(num);
//    int r = Integer.parseInt(s.substring(index, index+1));