#include <bits/stdc++.h>
using namespace std;
template <class T>
string toStr(const T &x) {
  stringstream s;
  s << x;
  return s.str();
}
template <class T>
int toInt(const T &x) {
  stringstream s;
  s << x;
  int r;
  s >> r;
  return r;
}
int dx[8] = {-1, -1, -1, 0, 1, 1, 1, 0};
int dy[8] = {-1, 0, 1, 1, 1, 0, -1, -1};
double d(double x1, double y1, double x2, double y2) {
  return sqrt(((x2 - x1) * (x2 - x1)) + ((y2 - y1) * (y2 - y1)));
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int r, x, y, x2, y2;
  cin >> r >> x >> y >> x2 >> y2;
  int ans = ceil(d(x, y, x2, y2) / (2.0 * r));
  cout << ans;
  return 0;
}
