#include <bits/stdc++.h>
using namespace std;
const double pi = 3.1415926535897932384626;
double s, r, R, n, f, v, c, l;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n >> R >> v;
  cout << fixed << setprecision(10);
  for (int i = 1; i <= n; i++) {
    cin >> s >> f;
    c = 2 * pi - fmod((f - s) / R, 2 * pi);
    c /= 2;
    l = pi;
    for (int j = 1; j <= 15; j++) l = l - (c - l + sin(l)) / (cos(l) - 1);
    if (pi - l < 0.00000001)
      cout << (f - s - 2 * R * (pi - l)) / v << endl;
    else
      cout << (f - s - 2 * R * sin(pi - l)) / v << endl;
  }
}
