#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double d = sqrt(pow(x - x1, 2) + pow(y - y1, 2));
  if (d == 0)
    cout << 0 << endl;
  else {
    int k = 1;
    while (d > (2 * k * r)) {
      k++;
    }
    cout << k << endl;
  }
  return 0;
}
