#include <bits/stdc++.h>
using namespace std;
int main() {
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
  float r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  float dist = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  dist = dist / (2 * r);
  int d = dist;
  if (d < dist) d++;
  cout << d;
  return 0;
}
