#include <bits/stdc++.h>
using namespace std;
inline long long read() {
  long long x = 0, f = 1;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  return x * f;
}
const double PI = 3.1415926535;
const double EPS = 5e-9;
int n, r, v;
int main() {
  cin >> n >> r >> v;
  for (int i = 1; i <= n; i++) {
    int s, f;
    scanf("%d %d", &s, &f);
    double dist = f - s;
    double t = floor(dist / (2 * PI * r));
    double remain = dist - t * 2 * PI * r;
    double lower = 0, upper = 2 * PI;
    while (lower + 1e-15 < upper) {
      double mid = (lower + upper) / 2;
      if (2 * sin(mid / 2) * r + mid * r < remain)
        lower = mid;
      else
        upper = mid;
    }
    double len = t * 2 * PI * r + upper * r;
    printf("%.12f\n", len / v);
  }
  return 0;
}
