#include <bits/stdc++.h>
using namespace std;
const long double pi = acos(-1);
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout << fixed << setprecision(9);
  int n;
  cin >> n;
  long double r, v;
  cin >> r >> v;
  long double w = v / r;
  for (int i = 0; i < n; i++) {
    long double s, f;
    cin >> s >> f;
    long double d = f - s;
    long double diff = d - 2 * pi * r * floor(d / 2 / pi / r);
    diff = 2 * pi * r - diff;
    long double start = diff / 2;
    long double low = 0, high = 1e10;
    for (int bs = 0; bs < 60; bs++) {
      long double mid = (low + high) / 2;
      long double travel = r * (w * mid - sin(w * mid));
      if (travel < start) {
        low = mid;
      } else {
        high = mid;
      }
    }
    long double disp = low;
    long double totd = 2 * pi * r * (floor(d / 2 / pi / r) + 1);
    long double overt = totd / v;
    long double res = overt - 2 * disp;
    cout << res << '\n';
  }
  return 0;
}
