#include<iostream>
#include<iomanip>
#include<cmath>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int N=1e5+10;
const int INF=0x3f3f3f3f;
int l,r;
int main(){
    cin >> l >> r;
    if (l * 2 <= r)
    {
        cout << r / 2;
        return 0;
    }
    for (int i = r - l;i >= 1;i--)
    {
        int num = r / i * i;
        if (l < num && l <= num - i)
        {
            cout << i;
            return 0;
        }
    }
    return 0;
}