#include <bits/stdc++.h>
using namespace std;
int main() {
  int x, y, x1, y1, r;
  scanf("%d %d %d %d %d", &r, &x, &y, &x1, &y1);
  float d = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  int num = ceil(d / (2 * r));
  printf("%d", num);
  return 0;
}
