#include <bits/stdc++.h>
using namespace std;
using std::map;
const int CMAX = 0;
int main() {
  int r, x, y, X, Y;
  double range;
  cin >> r >> x >> y >> X >> Y;
  range = sqrt((abs(x - X) * abs(x - X)) + (abs(y - Y) * abs(y - Y)));
  if (range - (int)range == 0.0 && (int)range % (2 * r) == 0.0)
    cout << (int)(range / (2 * r));
  else
    cout << (int)(range / (2 * r)) + 1;
  return 0;
}
