#include <iostream>

using namespace std;

int main()
{
    int n,m,r,egal,con;
    cin>>n;
    cin>>m;
    if(m>n)
    {
        con=m;
        m=n;
        n=con;
    }
    egal=1;
    con=0;
    while(egal!=0)
    {
        if((n+con)%(m+con)==0)
        {
            egal=0;
        }
        con++;
    }
    con--;
    cout<<con;
    return 0;
}