#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x1, y1, x2, y2, ans, r2;
  float d;
  scanf("%d%d%d%d%d", &r, &x1, &y1, &x2, &y2);
  r2 = 2 * r;
  d = sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2));
  ans = ceil(d / r2);
  printf("%d", ans);
  return 0;
}
