#include <bits/stdc++.h>
using namespace std;
int main() {
  ios ::sync_with_stdio(false);
  cin.tie(0);
  ;
  vector<long long int> u, v;
  map<long long int, long long int> mp;
  set<long long int> set;
  map<long long int, long long int>::iterator it;
  long long int x, y, z, c, d, e, f, g, h, i, j, k, l, n, m, o, p, q, r, t,
      ck = 0;
  string s, second;
  cin >> n >> p >> q >> r >> t;
  double dd = sqrt(pow((r - p), 2) + pow((t - q), 2));
  m = dd / (2 * n);
  if (m * 2 * n == dd)
    cout << m << "\n";
  else
    cout << m + 1 << "\n";
  return 0;
}
