#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0);
int main() {
  double s, f, r, v;
  int n;
  scanf("%d%lf%lf", &n, &r, &v);
  while (n--) {
    scanf("%lf%lf", &s, &f);
    double ans = 0, d = f - s;
    int cnt = (int)floor(d / (2 * pi * r));
    ans += cnt * 2 * pi * r / v;
    d -= cnt * (2 * pi * r);
    d /= 2;
    double L = 0, R = d;
    for (int _i = 0; _i < 60; _i++) {
      double mid = (L + R) / 2;
      if (mid + sin(mid / r) * r > d)
        R = mid;
      else
        L = mid;
    }
    ans += 2 * L / v;
    printf("%f\n", ans);
  }
  return 0;
}
