#include <bits/stdc++.h>
using namespace std;
void FastInputOutput() {
  ios_base ::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
}
int main() {
  int r, x1, y1, x2, y2;
  scanf("%d%d%d%d%d", &r, &x1, &y1, &x2, &y2);
  int p1 = (x2 - x1);
  int p2 = (y2 - y1);
  double ans = sqrt(p1 * p1 + p2 * p2);
  printf("%d", (int)ceil(ans / (2 * r)));
  return 0;
}
