#ifndef ABC
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <string>
#include <map>
#include <vector>
#include <algorithm>
#include <math.h>
#include <set>
#include <queue>
#include <stack>
#include <list>
#define endl '\n'
#define ABS(x) (((x)^((x) >> 31)) - ((x) >> 31))
#include <ctime>
using namespace std;

typedef long long ll;
typedef pair<ll, ll> pi;
typedef pair<pi, ll> ppi;
typedef vector<ll> vi;
typedef vector<vi> vvi;
typedef vector<pi> vpi;
typedef vector<vpi> vvpi;
typedef vector<ppi> vppi;
typedef vector<bool> vb;
typedef map<ll, ll> mii;
typedef set<pi> spi;
typedef set<ll> si;
typedef multiset<ll> msi;
typedef multiset<pi> mspi;
typedef vector<si> vsi;
template <typename T> using V = vector<T>;
template <typename T> using VV = vector<V<T>>;
template <typename T> using Mi = map<ll, T>;
template <typename T> using MMi = map<ll, Mi<T>>;

const double PI = 3.141592653589793238463;
#endif // ABC




void cinArr(vi &arr) {
	for (int i = 0; i < arr.size(); i++) {
		cin >> arr[i];
	}
}


int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cout.precision(15);

	ll a, b;
	cin >> a >> b;
	/*
	long double time = 0;
	ll N = 1e7;
	ll mn = 100;
	srand(unsigned(std::time(0)));
	for (int i = 0; i < N; i++) {
		ll x1, x2, y1, y2;
		x1 = rand() % (a*mn+ 1);
		x2 = rand() % (a*mn + 1);
		y1 = rand() % (b*mn + 1);
		y2 = rand() % (b*mn + 1);
		time += abs(x1 - x2) + abs(y1 - y2);
	}
	long double ans = time / (N*mn);
	cout << ans;
	*/
	cout <<fixed <<  (a+b)/3.0;
	//2 2 = 4/3
	//1 1 = 2/3
	//1 2 = 1
	//2 3 = 1.67? 5/3
	//1 4 = 1.67? 5/3
	return 0;
}