#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, a, b, c, d, t;
  double s;
  scanf("%d%d%d%d%d", &r, &a, &b, &c, &d);
  s = (c - a) * (c - a) + (d - b) * (d - b);
  s = sqrt(s);
  s = s / (r * 2);
  t = s;
  if (s - 2 * r * t == 0)
    printf("%d", t);
  else {
    printf("%d", t + 1);
  }
}
