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