#include <bits/stdc++.h>
using namespace std;
const double EPS = 1e-9;
double pi = abs(acos(-1));
double ff(double dist) {
  double goal = dist / 2;
  double lo = 0, hi = pi;
  for (int i = (int)(0); i < (int)(80); i++) {
    double mid = (lo + hi) / 2;
    if (mid + sin(mid) <= goal) {
      lo = mid;
    } else {
      hi = mid;
    }
  }
  return 2 * hi;
}
int main(void) {
  int n;
  double r, v;
  cin >> n >> r >> v;
  for (int i = (int)(0); i < (int)(n); i++) {
    double s, f;
    cin >> s >> f;
    s = f - s;
    double rot = floor(s / (2 * pi * r));
    double rem = s - rot * 2 * pi * r;
    printf("%.10f\n", (rot * 2 * pi + ff(rem / r)) * r / v);
  }
}
