#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, xf, yf, d, mov = 0;
  cin >> r >> x >> y >> xf >> yf;
  d = r * 2;
  float dist = sqrt((x - xf) * (x - xf) + (y - yf) * (y - yf));
  int dis = dist;
  mov = dist / d;
  if (dist / d != (int)(dis / d)) mov++;
  if (x == xf && y == yf)
    cout << 0;
  else
    cout << mov << endl;
  return 0;
}
