#include <bits/stdc++.h>
using namespace std;
const int N = 105;
long long r, x1, y11, x2, y2;
double dis() {
  return sqrt(double((x1 - x2) * (x1 - x2) + (y11 - y2) * (y11 - y2)));
}
int main() {
  while (cin >> r >> x1 >> y11 >> x2 >> y2) {
    double d = dis();
    long long ans = 0;
    while (d > 0) {
      d -= 2 * r;
      ans++;
    }
    cout << ans << endl;
  }
  return 0;
}
