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