#include <bits/stdc++.h>
using namespace std;
using namespace std::chrono;
template <typename A>
ostream &operator<<(ostream &cout, vector<A> const &v);
template <typename A, typename B>
ostream &operator<<(ostream &cout, pair<A, B> const &p) {
  return cout << "(" << p.first << ", " << p.second << ")";
}
template <typename A>
ostream &operator<<(ostream &cout, vector<A> const &v) {
  cout << "[";
  for (int i = 0; i < v.size(); i++) {
    if (i) cout << ", ";
    cout << v[i];
  }
  return cout << "]";
}
template <typename A, typename B>
istream &operator>>(istream &cin, pair<A, B> &p) {
  cin >> p.first;
  return cin >> p.second;
}
mt19937 rng(steady_clock::now().time_since_epoch().count());
void usaco(string filename) {
  freopen((filename + ".in").c_str(), "r", stdin);
  freopen((filename + ".out").c_str(), "w", stdout);
}
const long double pi = 3.14159265358979323846;
const long long mod = 1000000007;
long long n, m, k, q, Q, T, l, r, x, y, z;
long long a[1000005];
long long b[1000005];
long double c[1000005];
string second, t;
long long ans = 0;
double shoelace(double X[], double Y[], int n) {
  double area = 0.0;
  int j = n - 1;
  for (int i = 0; i < n; i++) {
    area += (X[j] + X[i]) * (Y[j] - Y[i]);
    j = i;
  }
  return abs(area / 2.0);
}
int main() {
  {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
  };
  for (int ele = 0; ele < 6; ele++) cin >> a[ele];
  ;
  double X[6], Y[6];
  double ang = 0;
  double x = 0, y = 0;
  for (long long i = 0; i < (6); i++) {
    X[i] = x;
    Y[i] = y;
    x += a[i] * cos(ang);
    y += a[i] * sin(ang);
    ang += pi / 3;
  }
  cout << (long long)(2 * shoelace(X, Y, 6) / 0.86602540378 + 0.5) << endl;
}
