#include <bits/stdc++.h>
using namespace std;
int n;
double r, v, ar;
inline double func(double x) { return r * (x - sin(x)); }
double arc(double x) {
  double k = floor(x / ar);
  double l = 2 * M_PI * k, r = 2 * M_PI * (k + 1);
  for (int i = 0; i < 100; i++) {
    double mid = (l + r) / 2.0;
    if (func(mid) <= x)
      l = mid;
    else
      r = mid;
  }
  return l;
}
int main() {
  scanf("%d %lf %lf", &n, &r, &v);
  ar = 2.0 * M_PI * r;
  for (int i = 0; i < n; i++) {
    double s, f, c, h, ss, ff, ans;
    scanf("%lf %lf", &s, &f);
    c = floor((f - s) / ar);
    h = (f - s - ar * c) / 2.0;
    ss = arc(M_PI * r - h);
    ff = arc(M_PI * r + h);
    ans = (ff - ss) * r / v + ar * c / v;
    printf("%.15f\n", ans);
  }
  return 0;
}
