#include <bits/stdc++.h>
using namespace std;
int r, x, y, u, v, ans;
double L;
int main() {
  scanf("%d%d%d%d%d", &r, &x, &y, &u, &v);
  L = sqrt((x - u) * (x - u) + (y - v) * (y - v));
  while (L > 0) {
    ans++;
    L -= 2 * r;
  }
  printf("%d\n", ans);
  return 0;
}
