#include <bits/stdc++.h>
using namespace std;
double l, d, v, g, r;
int main() {
  cin >> l >> d >> v >> g >> r;
  if (g * v > d) {
    printf("%.8f\n", l / v);
  } else {
    double ans = g;
    while (true) {
      if ((ans + r) * v >= d) {
        printf("%.8f\n", ans + r + (l - d) / v);
        break;
      } else if ((ans + r + g) * v > d) {
        printf("%.8f\n", ans + (l - (ans * v)) / v);
        break;
      }
      ans += (g + r);
    }
  }
  return 0;
}
