#include <bits/stdc++.h>
using namespace std;
long long getint() {
  long long _x = 0, _tmp = 1;
  char _tc = getchar();
  while ((_tc < '0' || _tc > '9') && _tc != '-') _tc = getchar();
  if (_tc == '-') _tc = getchar(), _tmp = -1;
  while (_tc >= '0' && _tc <= '9') _x *= 10, _x += (_tc - '0'), _tc = getchar();
  return _x * _tmp;
}
long long mypow(long long _a, long long _x, long long _mod) {
  if (_x == 0) return 1ll;
  long long _tmp = mypow(_a, _x / 2, _mod);
  _tmp = (_tmp * _tmp) % _mod;
  if (_x & 1) _tmp = (_tmp * _a) % _mod;
  return _tmp;
}
bool equal(double _x, double _y) { return _x > _y - 1e-9 && _x < _y + 1e-9; }
int __ = 1, cs;
int n;
double r, v, s, f;
const double Pi = acos(-1.0);
void build() {}
void init() {
  n = getint();
  r = getint();
  v = getint();
}
double dlt;
bool okay(double trnd) {
  double dx = trnd * 2 * Pi * r;
  double res = trnd - (double)((int)trnd);
  double deg = Pi * res;
  double dltx = sin(deg) * r;
  dx += 2.0 * dltx;
  return dx > dlt;
}
void solve() {
  while (n--) {
    s = getint();
    f = getint();
    dlt = f - s;
    double bl = 0, br = 1e20, bmid;
    for (int i = 0; i < 200; i++) {
      bmid = (bl + br) * 0.5;
      if (okay(bmid))
        br = bmid;
      else
        bl = bmid;
    }
    double rnd = v / (2 * Pi * r);
    printf("%.12f\n", bmid / rnd);
  }
}
int main() {
  build();
  while (__--) {
    init();
    solve();
  }
}
