#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x2, y2;
  cin >> r >> x >> y >> x2 >> y2;
  double dis2 = sqrt(pow(x2 - x, 2) + pow(y2 - y, 2));
  int dis = sqrt(pow(x2 - x, 2) + pow(y2 - y, 2));
  r *= 2;
  int ans = (dis) / r;
  if (dis % r == 0 && dis2 == dis) {
    cout << ans;
  } else {
    cout << ans + 1 << endl;
  }
}
