#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  float k = sqrt((float)(x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
  if (k < r)
    cout << 0;
  else
    cout << (int)k / r - 1;
  return 0;
}
