#include <fstream>
#include <iostream>
using namespace std;

long long cmmdc (int a,int b)
{
    if (b==0)
        return a;
    return cmmdc(b,a%b);
}



int main()
{
    ifstream f("cmmdc.in");
    ofstream g("cmmdc.out");
    long long a,b,c;
    f>>a>>b;
    if (a==0 || b==0)
        g<<a+b;
    else
    {
        c=cmmdc(a,b);
        if (c==1)
            g<<0;
        else
            g<<c;
    }
    return 0;
}