#include <bits/stdc++.h>
using namespace std;
int main() {
  float ray, x1, y1, x2, y2;
  int i = 0;
  cin >> ray >> x1 >> y1 >> x2 >> y2;
  float dis = sqrt(pow((x1 - x2), 2) + pow((y1 - y2), 2));
  while ((i * ray) < dis / 2) {
    i++;
  }
  cout << i;
}
