#include <bits/stdc++.h>
using namespace std;
double pi = acos(-1.0);
int f, t;
int r, v;
double d;
int m;
double ans;
double ret;
double calc(double x, double y) {
  double l, r, mid, ret;
  l = 0;
  r = pi;
  int times = 0;
  while (times <= 88) {
    mid = (l + r) / 2;
    if (x * (mid - sin(mid)) > y) {
      r = mid;
    } else
      l = mid;
    times++;
  }
  return mid;
}
int main() {
  scanf("%d%d%d", &m, &r, &v);
  for (int i = 1; i <= m; i++) {
    scanf("%d%d", &f, &t);
    d = t - f;
    int tims = floor(d / (2 * pi * r));
    ans = tims * (2 * pi * r / v);
    d = d - tims * (2 * pi * r);
    double fx = pi * r - d / 2;
    double theta = calc(r, fx);
    double omega = (double)v / r;
    ans = ans + (2 * pi * r / v) - theta / omega * 2;
    printf("%.10lf\n", ans);
  }
  return 0;
}
