#include <bits/stdc++.h>
const long double PI = acosl(-1);
int main() {
  int q, r, v;
  std::cin >> q >> r >> v;
  long double rr = r, vv = v;
  std::cout << std::fixed << std::setprecision(20);
  while (q--) {
    int s, f;
    std::cin >> s >> f;
    long double ans = 0.0;
    long double delta = (f - s) / rr;
    ans += (int)((delta) / (2 * PI));
    ans = ans * (2 * PI);
    delta -= ans;
    long double l = 0, r = 2 * PI;
    for (int i = 0; i < 100; i++) {
      long double mid = (l + r) / 2;
      if (mid - sinl(mid) > PI - delta / 2)
        r = mid;
      else
        l = mid;
    }
    long double add = 2 * (PI - l);
    ans += add;
    std::cout << (ans / (vv / rr)) << '\n';
  }
}
