#include <bits/stdc++.h>
using namespace std;
int main() {
  vector<pair<int, int> > a;
  long b, i, j, n, x, y, x1, y1;
  long k, r, mx;
  scanf("%ld", &r);
  scanf("%ld%ld", &x, &y);
  scanf("%ld%ld", &x1, &y1);
  mx = (x - x1) * (x - x1) + (y - y1) * (y - y1);
  n = sqrt(mx);
  k = n / (2 * r);
  if (n * n < mx && (2 * k * r) == n) k++;
  printf("%ld", k);
  return 0;
}
