#include <bits/stdc++.h>
using namespace std;
double pi = 3.14159265358979;
int n, R, v;
double s, f;
double half(double d) {
  double l = 0, r = 2 * pi;
  for (int i = (int)(0); i < (int)(60); i++) {
    double m = (l + r) / 2;
    if (m + sin(m) > d) {
      r = m;
    } else {
      l = m;
    }
  }
  return r;
}
int main(void) {
  cin >> n >> R >> v;
  double w = 2 * R * pi;
  while (n--) {
    cin >> s >> f;
    double d = f - s;
    int k = d / w;
    d -= k * w;
    double theta = half(d / w * pi);
    double ans = k * w / v + w / v * theta / pi;
    printf("%.8lf\n", ans);
  }
  return 0;
}
