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