#include <bits/stdc++.h>
using namespace std;
const long long mod1 = 1000000007;
const long long mod9 = 998244353;
long long powmod(long long a, long long b, long long mod = mod1) {
  long long ans = 1;
  while (b--) {
    ans = (ans * a) % mod;
  }
  return ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ;
  long long t = 1;
  while (t--) {
    double x1, y1, x2, y2, r;
    cin >> r >> x1 >> y1 >> x2 >> y2;
    cout << (ceil(sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)) /
                  (2 * r)))
         << "\n";
    ;
  }
  return 0;
}
