#include <bits/stdc++.h>
using namespace std;
const int N = 101000;
string s;
long long n, m, k;
vector<int> v;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  ;
  if (x == x1 && y == y1) {
    cout << 0 << endl;
    return 0;
  }
  long double dist = sqrt(((x - x1) * (x - x1)) + ((y - y1) * (y - y1)));
  cout << ceil(dist / (r * 2));
  return 0;
}
