Подскажите, что не так делаю?
package com.javarush.task.task14.task1420;
/*
НОД
*/
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class Solution {
public static void main(String[] args) throws Exception {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int a;
int b;
try {
a = Integer.parseInt(reader.readLine());
b = Integer.parseInt(reader.readLine());
if (a<=0||b<=0) throw new Exception();
while (a != 0 && b != 0) {
if (a > b) a %= b;
else b %= a;
}
System.out.println(a+b);
}
catch (Exception e) {
System.out.println("Не число!");
}
}
}