#include <bits/stdc++.h>
using namespace std;
int n, r, v, s, f;
double pai = acos(-1);
int main() {
  scanf("%d%d%d", &n, &r, &v);
  for (int i = 0; i < n; i++) {
    scanf("%d%d", &s, &f);
    double len = f - s;
    double c = pai * r * 2;
    int k = len / c;
    double ans = k * c / v;
    len -= c * k;
    len /= 2;
    double lef = 0, rig = len;
    for (int i = 0; i < 45; i++) {
      double mid = (lef + rig) / 2;
      if (mid + r * sin(mid / r) >= len)
        rig = mid;
      else
        lef = mid;
    }
    ans += 2 * lef / v;
    printf("%.15lf\n", ans);
  }
  return 0;
}
