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