#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:102400000,102400000")
template <class T>
inline void gmax(T &a, T b) {
  if (b > a) a = b;
}
template <class T>
inline void gmin(T &a, T b) {
  if (b < a) a = b;
}
using namespace std;
const int N = 1e5 + 10, M = 2e6 + 10, Z = 1e9 + 7, maxint = 2147483647,
          ms1 = 16843009, ms31 = 522133279, ms63 = 1061109567,
          ms127 = 2139062143;
const double PI = acos(-1.0), eps = 1e-8;
void fre() {
  freopen("/Users/luras/Desktop/in.txt", "r", stdin);
  freopen("/Users/luras/Desktop/out.txt", "w", stdout);
}
const int INF = 1e9;
int casenum, casei;
int n;
double l, r, mid, R, v, s, f, ans;
int cmp(double x, double y) {
  if (x - eps > y) return 1;
  if (x + eps < y) return -1;
  return 0;
}
int main() {
  while (~scanf("%d%lf%lf", &n, &R, &v)) {
    double C = 2 * PI * R;
    for (int i = 1; i <= n; i++) {
      scanf("%lf%lf", &s, &f);
      double dis = f - s;
      double ans = 0;
      int k = dis / C;
      dis -= k * C;
      dis /= 2;
      ans += k * C;
      l = 0, r = dis;
      for (int tim = 1; tim <= 100; tim++) {
        mid = (l + r) / 2;
        mid + R *sin(mid / R) >= dis ? r = mid : l = mid;
      }
      printf("%.15lf\n", (ans + 2 * l) / v);
    }
  }
  return 0;
}
