#include <bits/stdc++.h>
using namespace std;
int main() {
  double j, x, y, i, k, t, len, z, m, r, x1, y1, res;
  cin >> r >> x >> y >> x1 >> y1;
  k = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  k = k / (2 * r);
  res = ceil(k);
  if (res <= 0) {
    if (x == x1 && y == y1)
      cout << 0;
    else
      cout << 1;
  } else
    cout << res;
}
