#include<bits/stdc++.h>
#define int long long
using namespace std;
int a,b;
void solve(){
    cin>>a>>b;
    int c=b-a;
    while(true){
        if(a%c==0||b%c==0)break;
        if((b/c)-(a/c)>=2)break;
        c--;
    }
    cout<<c<<'\n';
}
signed main(){
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    solve();
}

//@Author: KeinYukiyoshi

// clang-format off
#include <bits/stdc++.h>
//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx")
#define int long long
using namespace std;
#define stoi stoll
#define fi first
#define se second
#define rep(i, n) for(int i=0, i##_len=(n); i<i##_len; i++)
#define rep2(i, a, b) for (int i = (int)(a), i##_len=(b); i < i##_len; i++)
#define rep3(i, a, b) for (int i = (int)(a), i##_len=(b); i >= i##_len; i--)
#define FOR(i, a) for (auto &i: a)
#define ALL(obj) begin(obj), end(obj)
#define _max(x) *max_element(ALL(x))
#define _min(x) *min_element(ALL(x))
#define _sum(x) accumulate(ALL(x), 0LL)

const int MOD   = 1000000007;
// const int MOD    = 998244353;
// const int INF    = (int)1e18;
// const int INF    = 10000000000007; // 1e13 + 7
// const int INF    = LLONG_MAX; // 9.2e18
const double EPS = 1e-8;
const double PI  = 3.14159265358979;
template <class T> using V = vector<T>;
template <class T> using VV = vector<vector<T>>;
template <class T> using VVV = vector<vector<vector<T>>>;
template <class T, class S>  using P = pair<T, S>;
template<class T> bool chmax(T &a, const T &b) {if (a < b) {a = b;return true;}return false;}
template<class T> bool chmin(T &a, const T &b) {if (b < a) {a = b;return true;}return false;}
int _ceil(int a, int b) { return (a >= 0 ? (a + (b - 1)) / b : (a - (b - 1)) / b); }
template<class T> T chmod(T &a, T mod=MOD) {a =  a >= 0 ? a % mod : a - (mod * _ceil(a, mod)); return a;};
int _mod(int a, int mod=MOD) {return a >= 0 ? a % mod : a - (mod * _ceil(a, mod));}
int _pow(int a, int b) {int res = 1;for (a %= MOD; b; a = a * a % MOD, b >>= 1)if (b & 1) res = res * a % MOD;return res;}
struct mint {long long x;mint(long long x = 0) : x((x % MOD + MOD) % MOD) {}mint operator-() const { return mint(-x); }mint &operator+=(const mint a) {if ((x += a.x) >= MOD) x -= MOD;return *this;}mint &operator-=(const mint a) {if ((x += MOD - a.x) >= MOD) x -= MOD;return *this;}mint &operator*=(const mint a) { (x *= a.x) %= MOD;return *this; }mint operator+(const mint a) const { return mint(*this) += a; }mint operator-(const mint a) const { return mint(*this) -= a; } mint operator*(const mint a) const { return mint(*this) *= a; }mint pow(long long t) const {if (!t) return 1;mint a = pow(t >> 1);a *= a;if (t & 1) a *= *this;return a;}mint inv() const { return pow(MOD - 2); }mint &operator/=(const mint a) { return *this *= a.inv(); }mint operator/(const mint a) const { return mint(*this) /= a; }};istream &operator>>(istream &is, mint &a) { return is >> a.x; }ostream &operator<<(ostream &os, const mint &a) { return os << a.x; }
// clang-format on
vector<int> divisor;
void enumerate_divisor(int n) {
  divisor = {};
  for (int i = 1; i <= (int)sqrt(n); i++) {
    if (n % i == 0) {
      divisor.emplace_back(i);
      if (i * i != n) divisor.emplace_back(n / i);
    }
  }
  sort(begin(divisor), end(divisor));
}
class CMaxGCD2 {
public:
  static void solve(istream &cin, ostream &cout) {
    cin.tie(nullptr);
    cout.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);
    int A, B;
    cin >> A >> B;
    V<int> yaku(300000 + 100);
    rep2(i, A, B + 1) {
      enumerate_divisor(i);
      FOR(j, divisor)
      yaku[j]++;
    }
    rep3(i, 300000 + 10, 1) {
      if (yaku[i] > 1) {
        cout << i << endl;
        return;
      }
    }
  }
};


signed main() {
  CMaxGCD2 solver;
  std::istream& in(std::cin);
  std::ostream& out(std::cout);
  solver.solve(in, out);
  return 0;
}

