#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, r, v;
  cin >> n >> r >> v;
  cout.precision(16);
  for (int i = 0; i < n; i++) {
    int d1, d2;
    cin >> d1 >> d2;
    int d = d2 - d1;
    double x = (d) / (2.0 * 3.14159265358979323846 * r);
    double t = (2 * 3.14159265358979323846 * r) * ((int)x);
    double rem = (3.14159265358979323846 * r) * (x - (int)x);
    double t1 = 0;
    double t2 = 3.14159265358979323846 * r;
    while (t2 - t1 > pow(10, -6)) {
      double mid = (t1 + t2) / 2;
      if (mid + r * sin(mid / r) > rem) {
        t2 = mid;
      } else
        t1 = mid;
    }
    t += t1 + t2;
    cout << t / v << endl;
  }
}
