#include <bits/stdc++.h>
using namespace std;
const int maxm = 2e5 + 10;
const int maxn = 1e5 + 10;
double pai = acos(-1.0);
int main() {
  int n;
  double r, v;
  while (~scanf("%d%lf%lf", &n, &r, &v)) {
    double st, ed;
    while (n--) {
      scanf("%lf%lf", &st, &ed);
      double len = ed - st;
      double c = pai * r * 2;
      int k = len / c;
      double ans = k * c / v;
      len -= c * k;
      len /= 2;
      double lef = 0, rig = len;
      double mid = (lef + rig) / 2;
      while (rig - lef > 1e-7) {
        mid = (lef + rig) / 2;
        if (mid + r * sin(mid / r) >= len)
          rig = mid;
        else
          lef = mid;
      }
      ans += 2 * lef / v;
      printf("%.8f\n", ans);
    }
  }
}
