#include <bits/stdc++.h>
using namespace std;
const int mod = (int)1e9 + 7;
double f(double O, double r, double d) { return r * O + r * sin(O) - d; }
double solve(double v, double r, double d) {
  int cnt = 0;
  double lb = 0, ub = 3.14159265, mid, val, val1, val2;
  while (lb <= ub && cnt++ < 70) {
    mid = (lb + ub) / 2;
    val = f(mid, r, d);
    val1 = f(lb, r, d);
    val2 = f(ub, r, d);
    if (val * val1 < 0) {
      ub = mid;
    } else {
      lb = mid;
    }
  }
  return (mid * r) / v;
}
int main() {
  int n, i, j, k;
  double m, ans, rem, r, v;
  cin >> n >> r >> v;
  while (n--) {
    scanf("%d%d", &i, &j);
    m = ((double)(j - i) / (2 * 3.14159265 * r));
    int x = floor(m);
    ans = (x * 2 * 3.14159265 * r) / v;
    rem = (double)(j - i) - 2 * 3.14159265 * r * x;
    rem = rem / 2;
    ans += (solve(v, r, rem) * 2);
    printf("%.15f\n", ans);
  }
}
