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