#include <bits/stdc++.h>
const double pi = atan(1.0) * 4;
int v, r, s;
int main() {
  int n;
  scanf("%d%d%d", &n, &r, &v);
  for (int i = 0; i < n; i++) {
    int f;
    scanf("%d%d", &s, &f);
    s = f - s;
    int rn = s / pi / 2 / r;
    double l = s - rn * (pi * 2 * r);
    double lo = 0, hi = pi;
    for (int j = 0; j < 70; j++) {
      double mid = (lo + hi) / 2;
      double lm = mid + sin(mid);
      if (lm * 2 * r < l) {
        lo = mid;
      } else {
        hi = mid;
      }
    }
    printf("%.12f\n", (2 * lo + pi * 2 * rn) * r / v);
  }
  return 0;
}
