#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-9;
int main() {
  int l, d, v, g, r;
  cin >> l >> d >> v >> g >> r;
  double t = 1. * d / v;
  double res = 0;
  while (t > g + r) {
    t -= g + r;
    res += g + r;
  }
  if (t > g - eps) {
    res += g + r;
  } else {
    res += t;
  }
  res += 1. * (l - d) / v;
  cout << fixed << setprecision(10) << res << endl;
}
