#include <bits/stdc++.h>
using namespace std;
const long double pi = 2 * acos(0);
int main() {
  ios_base::sync_with_stdio(false);
  int n;
  long double r, v;
  cin >> n >> r >> v;
  for (int i = 0; i < n; i++) {
    long double s, e;
    cin >> s >> e;
    long double rem = fmod(e - s, 2 * pi * r);
    rem /= 2;
    long double mn = 0, mx = 2 * pi * r;
    for (int i = 0; i < 100; i++) {
      long double md = (mn + mx) / 2;
      if (md + r * sin(md / r) >= rem)
        mx = md;
      else
        mn = md;
    }
    cout << fixed << setprecision(10) << (2 * mx + (e - s - 2 * rem)) / v
         << '\n';
  }
}
