#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:102400000,102400000")
using namespace std;
const int INF = 0x3f3f3f3f;
const long long INFF = 0x3f3f;
const double pi = acos(-1.0);
const double inf = 1e18;
const double eps = 1e-6;
const long long mod = 1e9 + 7;
const unsigned long long mx = 133333331;
inline void RI(int &x) {
  char c;
  while ((c = getchar()) < '0' || c > '9')
    ;
  x = c - '0';
  while ((c = getchar()) >= '0' && c <= '9') x = (x << 3) + (x << 1) + c - '0';
}
int main() {
  int n;
  double R, v;
  while (~scanf("%d%lf%lf", &n, &R, &v)) {
    while (n--) {
      double f, s;
      scanf("%lf%lf", &f, &s);
      double len = s - f;
      double ans = 0;
      double re = fmod(len, 2 * pi * R);
      ans += len - re;
      double l = 0, r = pi;
      re = 0.5 * re;
      while (R * l + R * sin(l) + eps < re) {
        double mid = (r + l) / 2;
        if (R * mid + R * sin(mid) <= re)
          l = mid;
        else
          r = mid;
      }
      while (true) break;
      ans += 2 * l * R;
      printf("%.12f\n", ans / v);
    }
  }
  return 0;
}
