#include <iostream>

#define ll long long
using namespace std;
ll r,a,b,j,i;
ll cmmdc(ll a,ll b)
{
    r = b%a;
    while(r!=0)
        b=a,a=r,r=b%a;
    return a;
}
int main()
{
    cin>>a>>b;
    for( i=b-a;i>=1;i--)
    {
        for( j=a;j<=b-i;j++)
        {
            if(cmmdc(j,j+i)==1)
            {
                cout<<i+1;
                return 0;
            }
        }
    }
    return 0;
}