#include <bits/stdc++.h>
using namespace std;
int main() {
  long double r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  long double dist = sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2));
  if ((2 * r) * (long int)(dist / (r * 2)) == dist) {
    cout << dist / (r * 2);
  } else {
    cout << (long int)(dist / (r * 2)) + 1;
  }
  return 0;
}
