#include <bits/stdc++.h>
int main() {
  int n, x, y, x1, y1;
  scanf("%d %d %d %d %d", &n, &x, &y, &x1, &y1);
  double s = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  int ans = s / (2 * n);
  if ((s - ans * 2 * n) > 0) ans++;
  printf("%d\n", ans);
}
