#include <bits/stdc++.h>
using namespace std;
long long n, m, ans;
string str;
long long solve() {
  long long r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double d = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  cout << ceil(d / (2 * r));
  return 0;
}
signed main() {
  ios::sync_with_stdio(0);
  long long t = 1;
  while (t--) solve();
  return 0;
}
