#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:1024000000,1024000000")
using namespace std;
template <class T>
inline bool read(T &n) {
  T x = 0, tmp = 1;
  char c = getchar();
  while ((c < '0' || c > '9') && c != '-' && c != EOF) c = getchar();
  if (c == EOF) return false;
  if (c == '-') c = getchar(), tmp = -1;
  while (c >= '0' && c <= '9') x *= 10, x += (c - '0'), c = getchar();
  n = x * tmp;
  return true;
}
template <class T>
inline void write(T n) {
  if (n < 0) {
    putchar('-');
    n = -n;
  }
  int len = 0, data[20];
  while (n) {
    data[len++] = n % 10;
    n /= 10;
  }
  if (!len) data[len++] = 0;
  while (len--) putchar(data[len] + 48);
}
int n, r, v;
int main() {
  scanf("%d %d %d", &n, &r, &v);
  while (n--) {
    int s, f;
    scanf("%d %d", &s, &f);
    long double dist = f - s;
    long double ans = 0;
    int k = (int)dist / (2 * acos(-1.0) * r);
    dist -= k * (2 * acos(-1.0) * r);
    ans += k * (2 * acos(-1.0) * r) / v;
    dist /= 2;
    long double L = 0.0, R = dist;
    int T = 60;
    while (T--) {
      long double mid = (L + R) / 2;
      if (mid + r * sin(mid / r) > dist)
        R = mid;
      else
        L = mid;
    }
    ans += 2 * L / v;
    printf("%.10lf\n", double(ans));
  }
  return 0;
}
