#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  double r, x, y, xnew, ynew;
  cin >> r >> x >> y >> xnew >> ynew;
  if (x == xnew && y == ynew) {
    cout << 0;
    return 0;
  }
  double dist = sqrt((xnew - x) * (xnew - x) + (ynew - y) * (ynew - y));
  cout << ceil(dist / (2 * r));
  return 0;
}
