#include <bits/stdc++.h>
using namespace std;
double dt(double x1, double y1, double x2, double y2) {
  double res;
  res = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  return res;
}
int main() {
  double x, y, x1, y1, r;
  while (scanf("%lf %lf %lf %lf %lf", &r, &x, &y, &x1, &y1) != EOF) {
    int ans;
    double d = r * 2;
    double len = dt(x, y, x1, y1);
    ans = len / d;
    if (d * ans < len) ans++;
    printf("%d\n", ans);
  }
  return 0;
}
