#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int r, x1, y1, x2, y2, num = 0;
  ;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  float dis;
  dis = sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2));
  if (dis == 0) {
    cout << 0;
  } else {
    while (1) {
      dis = dis - 2 * r;
      num++;
      if (dis <= 0) {
        break;
      }
    }
    cout << num;
  }
}
