#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  long double r, v;
  cin >> r >> v;
  for (int i = 0; i < n; ++i) {
    long double s, f;
    cin >> s >> f;
    long double d = (f - s) / 2;
    long double L = 0, R = d * 2, M, res;
    for (int i = 0; i < 100; ++i) {
      M = (L + R) / 2.;
      res = M + r * sin(M / r);
      if (res < d)
        L = M;
      else
        R = M;
    }
    long double c1 = L;
    L = 0;
    R = d * 2;
    for (int i = 0; i < 100; ++i) {
      M = (L + R) / 2.;
      res = M - r * sin(M / r);
      if (res < d)
        L = M;
      else
        R = M;
    }
    long double c2 = L;
    long double ans = min(c1, c2) * 2. / v;
    printf("%.15Lf\n", ans);
  }
  return 0;
}
