#include <bits/stdc++.h>
using namespace std;
int main() {
  int a[5], i;
  double d, r;
  for (i = 0; i < 5; i++) {
    cin >> a[i];
  }
  r = pow((double)(a[3] - a[1]), 2.0) + pow((double)(a[4] - a[2]), 2.0);
  d = sqrt(r);
  cout << ceil(d / (2 * a[0])) << endl;
  return 0;
}
