#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int r, x0, y0, x, y;
  cin >> r >> x0 >> y0 >> x >> y;
  double d = sqrt((x - x0) * (x - x0) + (y - y0) * (y - y0));
  if (d == 0) cout << 0;
  int c = d * 10;
  if (c % 10 == 0) {
    c /= 10;
    if (c % r == 0)
      cout << c / (2 * r);
    else
      cout << (c) / (2 * r) + 1;
  } else {
    c /= 10;
    cout << c / (2 * r) + 1;
  }
  return 0;
}
