#include <bits/stdc++.h>
using namespace std;
const int maxn = 100000 + 10;
int main() {
  int i, j, res, n, m;
  double r, x1, y1, x2, y2;
  while (scanf("%lf%lf%lf%lf%lf", &r, &x1, &y1, &x2, &y2) != EOF) {
    double d = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
    if (fabs(d) <= 1e-8) {
      printf("0\n");
      continue;
    }
    double t = d / 2 / r;
    if ((int)(t)*r * 2 < d)
      printf("%d\n", (int)t + 1);
    else
      printf("%d\n", (int)t);
  }
  return 0;
}
