#include <bits/stdc++.h>
using namespace std;
double r, x1, x2, y, y3;
int main() {
  cin >> r >> x1 >> y >> x2 >> y3;
  double d = sqrt((x2 - x1) * (x2 - x1) + (y3 - y) * (y3 - y));
  cout << ceil(d / (2 * r));
  return 0;
}
