#include <bits/stdc++.h>
using namespace std;
int main() {
  long b, i, j, x, y, x1, y1, m, p, r, l;
  float k, mx, n;
  scanf("%ld", &r);
  scanf("%ld%ld", &x, &y);
  scanf("%ld%ld", &x1, &y1);
  mx = (x - x1) * (x - x1) + (y - y1) * (y - y1);
  n = sqrt(mx);
  m = n;
  p = m / (2 * r);
  if (n > m && m % (2 * r) == 0) p++;
  printf("%ld ", p);
  return 0;
}
