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