#include <bits/stdc++.h>
using namespace std;
const long double eps = 1e-10L;
int main() {
  long long r, x, y, xx, yy;
  cin >> r >> x >> y >> xx >> yy;
  long long d = (x - xx) * (x - xx) + (y - yy) * (y - yy);
  long double dd = sqrt(1.0L * d);
  r = r + r;
  long double res = dd / (1.0L * r);
  long long p = (long long)res;
  if (fabs(1.0L * p * 1.0L * r - dd) > eps) p++;
  cout << p << endl;
  return 0;
}
