#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
long long mod = 1e9 + 7;
const long long e = 100001;
pair<long long, long long> arr[100001];
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  double r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double d1 = sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y));
  cout << ceil(d1 / (2 * r));
}
