#include <bits/stdc++.h>
using namespace std;
const long double PI = 3.1415926535897932384626433832795;
const long double EPS = 1e-11;
int n;
double s, f;
long double r, v;
long double l, ans;
int kd;
long double t2, L, R, M, alpha, first;
int main() {
  if (0) {
    freopen("z.in", "wt", stdout);
    int N = 100000, M = 1000000000;
    cout << N << ' ' << M << ' ' << M << endl;
    for (int i = 0; i < (N); i++) cout << "1 2" << endl;
  }
  cout << setiosflags(ios::fixed) << setprecision(10);
  cin >> n >> r >> v;
  l = 2 * M_PI * r;
  for (int i = 0; i < (n); i++) {
    scanf("%lf%lf", &s, &f);
    f = f - s, s = 0;
    kd = (f - s) / l + 1e-15;
    ans = kd * l / v;
    f -= kd * l;
    t2 = (l / v) / 2;
    L = 0, R = t2;
    while (R - L > 1e-10) {
      M = (L + R) / 2;
      alpha = M_PI * (M / t2);
      first = v * M + r * sin(alpha);
      if (first > f / 2)
        R = M;
      else
        L = M;
    }
    printf("%.10le\n", (double)(ans + 2 * L));
  }
  return 0;
}
