#include <bits/stdc++.h>
using namespace std;
const long double pi = acos(-1);
long long a[20002][4] = {};
long long b[200002] = {};
string s = "", ss = "";
long long n, m, k, w;
long long ans;
long long mod = 1e9 + 7;
int main() {
  cin.tie(0);
  cin.sync_with_stdio(0);
  int t = 1;
  while (t--) {
    long double r, x1, x2, y1, y2;
    cin >> r >> x1 >> y1 >> x2 >> y2;
    long double d = sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2));
    cout << fixed << setprecision(0) << ceil(d / (2 * r));
  }
  return 0;
}
