#include <bits/stdc++.h>
using namespace std;
int main() {
  long long r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double dis = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  double res = dis / (r * 2);
  if (res == (long long)res)
    cout << (long long)res << endl;
  else
    cout << (long long)res + 1 << endl;
  return 0;
}
