#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double distance = sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
  if (distance == 0) {
    cout << 0;
    return 0;
  }
  if (distance <= 2 * r) {
    cout << 1;
    return 0;
  }
  double midDistance = distance - (2 * r);
  double x = midDistance / (2 * r);
  int y = x;
  int z = ceil(x);
  if ((z - y) == 0) {
    cout << y + 1;
    return 0;
  } else {
    cout << y + 2;
  }
  return 0;
}
