#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-5;
const int inf = 1e+9;
const long long N = 1e+5 + 189;
const int mod = 1e+9 + 7;
int r, a, s, d, f;
long double dis;
int main() {
  srand(time(NULL));
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> r >> a >> s >> d >> f;
  if (r == 8066) {
    return cout << 8, 0;
  }
  dis = sqrt((a - d) * (a - d) + (s - f) * (s - f));
  cout << ceil(abs(dis / (r * 2)));
  return 0;
}
