import java.math.BigInteger;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
BigInteger a = sc.nextBigInteger();
BigInteger b = sc.nextBigInteger();
BigInteger res = a.multiply(b).divide(a.gcd(b)).subtract(a.add(b));
System.out.println(res);
}
}