#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int r, x, y, xx, yy;
  cin >> r >> x >> y >> xx >> yy;
  double dist, temp;
  dist = sqrt((xx - x) * (xx - x) + (yy - y) * (yy - y));
  long long int ans;
  temp = dist / (2 * r);
  ans = temp;
  if ((temp - ans) > 0)
    cout << (ans + 1);
  else
    cout << ans;
  return 0;
}
