#include <bits/stdc++.h>
using namespace std;
int n, r, v, s, f;
double nowans, dis;
int main() {
  scanf("%d%d%d", &n, &r, &v);
  for (int i = 1; i <= n; i++) {
    scanf("%d%d", &s, &f);
    dis = f - s - 2 * acos(-1.0) * r * (int)((f - s) / (2 * acos(-1.0) * r));
    dis /= 2;
    nowans = 0;
    double L = 0, R = 2 * acos(-1.0) * r;
    for (int cnt = 1; cnt <= 100; cnt++) {
      double mid = (L + R) / 2;
      if (mid + r * sin(mid / r) >= dis)
        R = mid - 1e-8, nowans = mid;
      else
        L = mid + 1e-8;
    }
    nowans = 2 * nowans +
             2 * acos(-1.0) * r * ((int)((f - s) / (2 * acos(-1.0) * r)));
    printf("%.10lf\n", nowans / v);
  }
}
