#include <iostream>

using namespace std;
int cmmdc(int a,int b)
{
    while(a!=b)
    {
        if(a>b) a-=b;
        else b-=a;
    }
    return a;
}
int main()
{
    long long int a,b;
    cin>>b>>a;
    int ok=1;
    for(long long int i=a;i>=b && ok==1;i--)
    {
        for(long long int j=b;j<=i && ok==1;j++)
            if(cmmdc(i,j)==1)
            {
                cout<<i-j+1;
                ok=0;
            }
    }
    return 0;
}