#include <bits/stdc++.h>
using namespace std;
int main() {
  int ans;
  double d;
  int x1, x2, y1, y2, x, y, n, r;
  scanf("%d %d %d %d %d", &r, &x1, &y1, &x2, &y2);
  d = sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
  if ((int)d - d == 0) {
    ans = (int)d / (2 * r);
  } else
    ans = (int)d / (2 * r) + 1;
  printf("%d\n", ans);
}
