#include <bits/stdc++.h>
const int INF = 0x3f3f3f3f;
const int N = 201000;
const double eps = 1e-6;
using namespace std;
int n, r, v;
int eq(double a, double b) {
  if (b - a > eps)
    return -1;
  else if (a - b > eps)
    return 1;
  return 0;
}
int main() {
  while (scanf("%d%d%d", &n, &r, &v) == 3) {
    int s, f;
    while (n--) {
      scanf("%d%d", &s, &f);
      double fs = (double)(f - s) / 2;
      double x = 0, y = fs + r, m;
      while (y - x > eps) {
        m = (x + y) / 2;
        if (eq(m + r * sin(m / r), fs) == 0)
          break;
        else if (eq(m + r * sin(m / r), fs) == -1)
          x = m;
        else
          y = m;
      }
      double ans = m;
      x = 0, y = fs + r, m;
      while (y - x > eps) {
        m = (x + y) / 2;
        if (eq(m - r * sin(m / r), fs) == 0)
          break;
        else if (eq(m - r * sin(m / r), fs) == -1)
          x = m;
        else
          y = m;
      }
      ans = ((ans) < (m) ? (ans) : (m));
      printf("%.15lf\n", 2 * ans / v);
    }
  }
  return 0;
}
