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