#include <bits/stdc++.h>
using namespace std;
const double PI = 3.14159265359;
int main() {
  int n, r, v;
  cin >> n >> r >> v;
  while (n--) {
    int s, f;
    cin >> s >> f;
    double d = f - s;
    double o = 2 * r * PI;
    double lo = d - o, hi = d + o;
    for (int iter = 0; iter < 100; ++iter) {
      double mid = (lo + hi) / 2;
      if (mid + 2 * r * abs(sin(mid / (2 * r))) < d)
        lo = mid;
      else
        hi = mid;
    }
    cout.precision(10);
    cout << hi / v << endl;
  }
  return 0;
}
