#include <bits/stdc++.h>
using namespace std;
int question, r, speed, st, en, len, did;
double lft, rht, middle, dist, p;
inline double euclid_dist(double a, double b) { return sqrt(a * a + b * b); }
inline bool check(double dis) {
  p = 1.0 * dis / r;
  return r * euclid_dist(1 - cos(p), sin(p)) >= len - dis;
}
int main() {
  scanf("%d%d%d", &question, &r, &speed);
  for (register int i = 1; i <= question; i++) {
    scanf("%d%d", &st, &en);
    len = en - st;
    lft = 0;
    rht = len;
    did = 0;
    while (lft < rht && did <= 50) {
      middle = (lft + rht) / 2.0;
      switch (check(middle)) {
        case true:
          dist = middle;
          rht = middle;
          break;
        case false:
          lft = middle;
          break;
      }
      did++;
    }
    dist /= speed;
    printf("%0.12lf\n", dist);
  }
  return 0;
}
