#include<bits/stdc++.h>
#define int long long
using namespace std;

int L, R;

signed main() {
    cin >> L >> R;
    for(int i = L;; i++)
        for(int j = R;; j--)
            if(__gcd(i, j) == 1ll) {
                cout << j - i << endl;
                return 0;
            }
}