#include <bits/stdc++.h>
using namespace std;
int main() {
  long long r, x, y, x1, y1, c;
  cin >> r >> x >> y >> x1 >> y1;
  long long a = ((x - x1) * (x - x1)) + ((y - y1) * (y - y1));
  double d = sqrt(double(a));
  long long k = d / (2 * r);
  long long td = k * 2 * r;
  if ((d - td) == 0) {
    c = k;
  } else {
    c = k + 1;
  }
  cout << c;
  return 0;
}
