#include <bits/stdc++.h>
using namespace std;
int main(void) {
  double l, d, v, g, r;
  double res;
  double time = 0;
  cin >> l >> d >> v >> g >> r;
  res = d / v;
  while (true) {
    if (res < time) {
      res = time;
      break;
    }
    time += g;
    if (res < time) break;
    time += r;
  }
  res += (l - d) / v;
  printf("%.9f", res);
}
