#include <bits/stdc++.h>
using namespace std;
void solve();
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  long long t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
void solve() {
  int r, x1, x2, y1, y2, step;
  double dis;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  dis = sqrt(pow((x2 - x1), 2) + pow((y2 - y1), 2));
  step = dis / (2 * r);
  double rem = dis - step * 2 * r;
  if (rem != 0) step++;
  cout << step;
}
