I got an error when using nextInt, nextLine and substring.

import java.util.Scanner;

/*
The cause is nextInt
If you enter 123 in nextInt
123 on the Java side\Converted to n (at the end\n is entered. )
nextInt returns only 123
Next, when you enter nextLine, it remains\n is read
An error occurs.

The solution is
Write nextLine without assignment to a variable. (Scanner from the following sources.nextLine()）
By doing this\n is erased and nextLine works fine

* NextInt\Since there is no function to erase n, it is necessary to insert nextLine.
* Backslash and n represent line breaks.

*/
public class Hello {
    public static void main(String[] args) {
    	Scanner scanner = new Scanner(System.in);

        int a = 0;
        int b = 0;
        String str = "";

        a = scanner.nextInt();
        b = scanner.nextInt();
        scanner.nextLine();
        str = scanner.nextLine();
        System.out.println(str.substring(a - 1, b));
    }
 }

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