#include <bits/stdc++.h>
using namespace std;
double dis;
long long r, x, y, x2, y2, kol;
int main() {
  cin >> r >> x >> y >> x2 >> y2;
  dis = sqrt(((x2 - x) * (x2 - x)) + ((y2 - y) * (y2 - y)));
  while (dis > 0) dis -= 2 * r, kol++;
  cout << kol;
  return 0;
}
