#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0);
template <typename T, typename U>
inline void amin(T &x, U y) {
  if (y < x) x = y;
}
template <typename T, typename U>
inline void amax(T &x, U y) {
  if (x < y) x = y;
}
long long sqr(long long x) { return x * x; }
int Solve() {
  long long r, x[2], y[2];
  cin >> r;
  r *= 2;
  for (int i = 0; i < 2; i += 1) cin >> x[i] >> y[i];
  long long kc = ceil(sqrt(1.0 * sqr(x[0] - x[1]) + sqr(y[0] - y[1])));
  long long Move = (kc + r - 1) / r;
  cout << Move;
  return 0;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  int t = 1;
  while (t--) {
    Solve();
  }
  return 0;
}
