#include <bits/stdc++.h>
const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, 1, 0, -1};
using namespace std;
const long double PI = acos(-1.0);
int n, r, v;
inline long double calc(long double theta) { return r * (theta - sin(theta)); }
int main() {
  cin >> n >> r >> v;
  while (n--) {
    int s, f;
    scanf("%d%d", &s, &f);
    long double d = f - s;
    long long ni = d / (2 * PI * r);
    long double D = (1 + ni) * (2 * PI * r) - d;
    if (D > 2 * PI * r) D -= 2 * PI * r;
    long double low = 0, high = PI;
    for (int i = 0; i < 60; i++) {
      long double med = (high + low) / 2;
      if (2 * calc(med) > D)
        high = med;
      else
        low = med;
    }
    long double theta = (low + high) / 2;
    d -= 2 * r * sin(theta);
    double ans = d / v;
    printf("%.10lf\n", ans);
  }
  return 0;
}
