#include <bits/stdc++.h>
int main() {
  double r, x1, y1, x2, y2, ans, tot, d, l, h, m;
  int ansf;
  scanf("%lf %lf %lf %lf %lf", &r, &x1, &y1, &x2, &y2);
  tot = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
  l = 0;
  h = tot;
  m = (h + l) / 2;
  while (1) {
    m = (h + l) / 2;
    if (m * m > tot) {
      if (m * m - tot < 0.00000001)
        break;
      else
        h = m;
    } else if (m * m < tot) {
      if (tot - m * m < 0.00000001)
        break;
      else
        l = m;
    } else
      break;
  }
  tot = m;
  d = 2 * r;
  ans = (tot + d) / d;
  ansf = ans;
  printf("%d", ansf);
  return 0;
}
