#include <bits/stdc++.h>
using namespace std;
int main() {
  float r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  float steps;
  float d = (sqrt((pow((x2 - x1), 2)) + (pow((y2 - y1), 2))));
  float diameter = 2 * r;
  if (d == floor(d)) {
    steps = ((floor(d) / diameter)) + 1;
  } else if (d > floor(d)) {
    steps = (floor(d) / diameter) + 1;
  }
  cout << steps << "\n";
  return 0;
}
