ABC_211_A.cpp

//<---------------------Kamlesh Singh Bisht--------------------->
//AtCoder-Template
#include <bits/stdc++.h>
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL);
#define cstrt clock_t start, end; double ctd; start = clock();
#define cend end = clock(); ctd = ((double) (end - start)) / CLOCKS_PER_SEC;cout<<ctd<<"sec"<<endl;
#define rep(i,n,s) for(int i=0;i<n;i+=s)
#define fr(i,n,s) for(int i=1;i<=n;i+=s)
#define nl '\n'
#define dbg(x) cout<<#x<<"->"<<x<<nl;
#define ebg(x,y) cout<<#x<<"->"<<x<<" "<<#y<<"->"<<y<<nl;
#define int long long
#define mod 1000000007
#define pi pair<int,int>
#define vi vector<int>
#define vii vector<pi>
#define pb push_back
#define a first
#define b second
using namespace std;
//<-------------------------------CODE------------------------------->
void solve()
{
	int a, b; cin >> a >> b;
	float c = ((a - b) / 3.00000) + b;
	printf("%0.8f\n", c);
}

int32_t main()
{
	fastio;
	solve();
	return 0;
}