import java.io.*;
import java.util.*;
public class Main {
    static long gcd(long a, long b){ return (b==0) ? a : gcd(b, a%b); }
    static int gcd(int a, int b){ return (b==0) ? a : gcd(b, a%b); }
    public static void main(String args[]) {
        Scanner in = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
        long n = in.nextLong();
        long k = in.nextLong();
        long ans = gcd(n,k);
        System.out.println(find(n,k));
    }
    static long find(long n,long k){
        if(Math.abs(n-k)<n) return find((long)Math.min(n%k,k%n), k);
        return n;
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz