#include <bits/stdc++.h>
using namespace std;
namespace WorkSpace {
const double pi = acos(-1.0);
int N;
double r, v;
bool Check(double mid, double l) {
  double len = 2 * pi * r;
  double ang = mid / len * 2 * pi;
  double A = r - r * (cos(ang));
  double B = r * sin(ang);
  return sqrt(A * A + B * B) + mid > l;
}
void Deal(double s, double t) {
  double l = 0, r = t - s;
  double mid;
  int Cnt = 0;
  while (Cnt <= 40) {
    ++Cnt;
    mid = (l + r) / 2;
    if (Check(mid, t - s))
      r = mid;
    else
      l = mid;
  }
  printf("%.10lf\n", l / v);
}
void Main() {
  scanf("%d%lf%lf", &N, &r, &v);
  while (N--) {
    double s, t;
    scanf("%lf%lf", &s, &t);
    Deal(s, t);
  }
  return;
}
}  // namespace WorkSpace
int main() { WorkSpace ::Main(); }
