#include <bits/stdc++.h>
using namespace std;
double r, x, y, xx, yy, dis;
int main() {
  scanf("%lf %lf %lf %lf %lf", &r, &x, &y, &xx, &yy);
  dis = sqrt((xx - x) * (xx - x) + (yy - y) * (yy - y));
  printf("%g\n", ceil(dis / (2 * r)));
  return 0;
}
