#include <bits/stdc++.h>
using namespace std;
class TaskB {
 public:
  void solve(std::istream& in, std::ostream& out) {
    int n, r, v;
    in >> n >> r >> v;
    for (int i = 0; i < n; ++i) {
      int s, f;
      in >> s >> f;
      double L = 0, R = 1e9;
      for (int it = 0; it < 100; ++it) {
        double m = (L + R) / 2;
        double d = abs(2 * sin(m / 2)) * r + m * r;
        if (d >= f - s) {
          R = m;
        } else
          L = m;
      }
      out << L * r / v << "\n";
    }
  }
};
int main() {
  std::ios_base::sync_with_stdio(false);
  TaskB solver;
  std::istream& in(std::cin);
  std::ostream& out(std::cout);
  in.tie(0);
  out << std::fixed;
  out.precision(20);
  solver.solve(in, out);
  return 0;
}
