#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 5;
int main(void) {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  cerr.tie(nullptr);
  long long r = 0, x = 0, y = 0, p = 0, q = 0;
  cin >> r >> x >> y >> p >> q;
  if (x == p and y == q) {
    cout << 0 << endl;
    return 0;
  }
  long long d = hypot(x - p, y - q);
  long long cnt = 2;
  while (cnt * r < d) {
    cnt++;
  }
  cout << cnt - 1 << endl;
  return 0;
}
