#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

int main()
{
  int A, B;
  cin >> A >> B;

  int mn = A + B + A;
  int mx = A + B + B;

  int left = (mn-1) / 3;
  int right = mx / 3;

  cout << right - left << endl;
}