#include <bits/stdc++.h>
using namespace std;
const long long inf = 1e9 + 7;
const long double Pi = acos(-1);
const int N = 1;
void solve() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double d = sqrt(abs(x - x1) * abs(x - x1) + abs(y - y1) * abs(y - y1));
  int td = d / (2 * r);
  d /= double(2 * r);
  cout << (d - td ? td + 1 : td) << "\n";
  return;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  while (t--) solve();
  return 0;
}
