#include <bits/stdc++.h>
using namespace std;
int main() {
  unsigned int bite;
  long long r, x1, y1, x2, y2, n, t, c, previous, counter = 0, sum = 0, min = 0,
                                                  first = 1, last = 1;
  int hmaf = 0;
  bool flag = false;
  bool flag2 = false;
  double max = 0;
  map<string, string> mapnigga;
  map<string, string> maphomie;
  string str, str1, str2;
  int carr[28];
  int temp;
  char tempc;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  cout << ceil((sqrt(pow(y2 - y1, 2.0) + pow(x2 - x1, 2.0)) / r) / 2);
  return 0;
}
