#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll ceildiv(ll a, ll b) { return a / b + (a % b && (a ^ b) >= 0); }
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  ll n, m;
  cin >> n >> m;
  auto ch = [&](ll k) {
    ll rem = max<ll>(0, n - k * 4) + max<ll>(0, m - k * 4);
    return rem <= k;
  };
  ll ng = 0;
  ll ok = 1000000;
  while (ok - ng > 1) {
    ll mid = (ng + ok) / 2;
    (ch(mid) ? ok : ng) = mid;
  }
  cout << ok * 2 - 1 << "\n";
  return 0;
}