#include <bits/stdc++.h>
using namespace std;
int main() {
  double r, x, y, xx, yy, d, ans;
  cin >> r >> x >> y >> xx >> yy;
  d = sqrt(pow(xx - x, 2) + pow(yy - y, 2));
  r *= 2;
  ans = d / r;
  if (ans != (int)ans) {
    cout << ((int)ans + 1);
  } else {
    cout << ans;
  }
  return 0;
}
