#include <bits/stdc++.h>
using namespace std;
long long bp(long x) { return (long long)x * x; }
int main() {
  long r, x1, x2, y1, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  long long tmp = bp(y2 - y1) + bp(x2 - x1);
  r *= 2;
  if (sqrt(tmp) * sqrt(tmp) == tmp)
    tmp = sqrt(tmp);
  else
    tmp = sqrt(tmp) + 1;
  cout << (tmp + r - 1) / r;
}
