#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
using namespace std;
using ll = long long;
using P = pair<int,int>;

int main() {
  double a, b, c, d, e, f;
  cin >> a >> b >> c >> d >> e >> f;
  double r = sqrt(4*a*f - 4*a*e + c*c + d*d) / 2 / a;
  printf("%.5f\n", r);
  return 0;
}