#include <bits/stdc++.h>
using namespace std;
int main() {
  long long x1, y1, x2, y2, r;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  long long dist = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
  long long steps = ceil(sqrt((float)dist / (r * r)) / 2);
  cout << steps;
  return 0;
}
