Подскажите)
package com.javarush.task.task14.task1420;
import java.io.BufferedReader;
import java.io.InputStreamReader;
/*
НОД
*/
public class Solution {
public static void main(String[] args) throws Exception {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int a = Integer.parseInt(reader.readLine());
int b = Integer.parseInt(reader.readLine());
if (a < 1 && b < 1) throw new IllegalArgumentException();
int res = 0;
for (int i = 1; i < 24; i ++) {
if (a%i == 0 && b%i == 0) res = i;
}
System.out.println(res);
}
}