#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
int main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long tests = 1;
  while (tests--) {
    long long r, x, y, x1, y1;
    cin >> r >> x >> y >> x1 >> y1;
    double d = sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y));
    cout << ceil(d / ((double)(2 * r))) << endl;
  }
  return 0;
}
