#include <bits/stdc++.h>
using namespace std;
const long long INF = 1e9 + 7;
const int N = 2e2 + 10;
int main() {
  int l, d, v, g, r;
  cin >> l >> d >> v >> g >> r;
  double cost = 0;
  int cur = 0;
  while (1) {
    if (cur + v * g > d) {
      printf("%.14f\n", cost + 1.0 * (l - cur) / v);
      break;
    }
    cost += g;
    cur += v * g;
    cur += v * r;
    cost += r;
    cur = min(cur, d);
  }
  return 0;
}
