#include <bits/stdc++.h>
using namespace std;
int main() {
  unsigned long long r, x, y, a, b;
  cin >> r >> x >> y >> a >> b;
  float d;
  int aux;
  float aux2;
  d = sqrt((unsigned long long)(a - x) * (a - x) +
           (unsigned long long)(b - y) * (b - y));
  if (d == 0) {
    cout << 0 << endl;
    return 0;
  }
  if (d == 2 * r) {
    cout << 1 << endl;
    return 0;
  }
  aux = d / (2 * r);
  aux2 = (float)aux;
  if (d - aux2 > r) aux++;
  cout << aux << endl;
  return 0;
}
