#include <iostream>
#include <iomanip>
#include <stdio.h>
#include <string>
#include <vector>
#include <set>
#include <cmath>
#include <algorithm>
#define MP make_pair
using ll = long long;
using namespace std;

int main()
{
  int N,M;
  cin >> M >> N;
  double s = (2*M + M+1) / 3.0;
  cout << setprecision(20) << s + 1.0/3.0*(N-1) << endl;
  return 0;
}