#include <bits/stdc++.h>
using namespace std;
template <class T>
inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
using ll = long long;
const vector<int> dx = {1, 0, -1, 0};
const vector<int> dy = {0, 1, 0, -1};
const double PI = 3.1415926535;
const ll inf = 1001001001;
const ll e9 = 1000000000;
const ll mod = 1000000007;
const int MAX = 1000000;
const int MOD = 1000000007;
int main() {
  double n, x;
  cin >> n >> x;
  cout << fixed << setprecision(10) << n + (x * 7) / 2 << endl;
}
