#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int t = 1;
  while (t--) {
    long long r, x1, x2, y1, y2;
    cin >> r >> x1 >> y1 >> x2 >> y2;
    double dist = sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
    long long ans = dist / (2 * r);
    if (ans * 2 * r == dist)
      cout << ans;
    else
      cout << ans + 1;
    cout << "\n";
  }
  return 0;
}
