#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
  double n, m, s, a, b, f, c = 0, d, ans, r, test, sum = 0, sum1 = 0, i, j, l,
                           array[100000 + 10];
  string str;
  double db;
  cin >> r >> a >> b >> c >> d;
  test = (a - c) * (a - c) + (b - d) * (b - d);
  n = sqrt(test);
  ans = ceil(n / (2 * r));
  cout << ans << endl;
}
