#include <bits/stdc++.h>
using namespace std;
void solve() {
  long long n, a, b, x, y;
  cin >> n >> a >> b >> x >> y;
  cout << ceil(hypot(x - a, y - b) / (2 * n));
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  long long test;
  test = 1;
  while (test--) {
    solve();
  }
  return 0;
}
