#include <bits/stdc++.h>
using namespace std;
double l, d, v, g, r;
int main() {
  cin >> l >> d >> v >> g >> r;
  double mn = 1e8;
  for (double i = 1; i <= v; i++) {
    double kol = d / i;
    double yp = 0;
    double kol2 = kol;
    while (kol2 >= (r + g)) {
      kol2 -= (r + g);
      yp++;
    }
    if (kol - yp * (r + g) < g) {
      mn = min(mn, kol + (l - d) / v);
    } else {
      kol = kol - (kol - (yp * (r + g)) - g);
      mn = min(mn, kol + r + (l - d) / v);
    }
  }
  cout << fixed << setprecision(6) << mn;
}
