#include <bits/stdc++.h>
using namespace std;
void solve() {
  long long int r, xi, yi, xf, yf;
  cin >> r >> xi >> yi >> xf >> yf;
  double d = sqrt((xi - xf) * (xi - xf) + (yi - yf) * (yi - yf));
  cout << ceil(d / (2 * r));
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  solve();
  return 0;
}
