#include <bits/stdc++.h>
using namespace std;
inline bool EQ(double a, double b) { return fabs(a - b) < 1e-9; }
inline int gcd(int a, int b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
template <typename T>
string to_str(T str) {
  stringstream stream;
  stream << str;
  return stream.str();
}
template <typename T>
int to_int(T num) {
  int val;
  stringstream stream;
  stream << num;
  stream >> val;
  return val;
}
vector<string> split(const string& s, char delim) {
  vector<string> elems;
  stringstream ss(s);
  string item;
  while (getline(ss, item, delim)) elems.push_back(item);
  return elems;
}
const int dr[] = {-1, -1, 0, 1, 1, 1, 0, -1};
const int dc[] = {0, 1, 1, 1, 0, -1, -1, -1};
int main() {
  ios_base::sync_with_stdio(0);
  long long int r, x, y, x1, y1, ans;
  cin >> r >> x >> y >> x1 >> y1;
  ans = ceil(sqrt(((x1 - x) * (x1 - x)) + ((y1 - y) * (y1 - y))) / (2 * r));
  cout << ans << endl;
  return 0;
}
