#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, a, b;
  cin >> r >> x >> y >> a >> b;
  double dist = sqrt((a - x) * (a - x) + (y - b) * (y - b));
  if (dist == 0) {
    cout << 0;
    return 0;
  }
  int ans = 0;
  while (dist > 0) {
    ans++;
    dist -= 2 * r;
  }
  cout << ans;
  return 0;
}
