#include <bits/stdc++.h>
using namespace std;
int main() {
  long long r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double d1 = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  double d2 = d1 / (2 * r);
  if (d2 == (long long)d2)
    cout << d2;
  else
    cout << (long long)d2 + 1;
}
