Подскажите с исключениями

package com.javarush.task.task14.task1420;

/*
НОД
*/

import java.io.BufferedReader;
import java.io.IOException;
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 = 0, b = 0, min = 0, i = 2, Nod = 1;
        String n;

             n = reader.readLine();
             a = Integer.parseInt(n);
             n = reader.readLine();
             b = Integer.parseInt(n);


             if (a < 0) throw new Exception();
             if (b < 0) throw new Exception();


             if (a < b)
                 min = a;
             else min = b;
             while (i <= min) {
                 if ((a % i == 0) && (b % i == 0)) {
                     Nod = Nod * i;
                     a = a / i;
                     b = b / i;
                 } else i++;
             }
             System.out.println(Nod);

    }
    }