#include <bits/stdc++.h>
int main() {
  unsigned int r = 0;
  int x0 = 0, y0 = 0, x1 = 0, y1 = 0;
  std::scanf("%u%d%d%d%d", &r, &x0, &y0, &x1, &y1);
  const double dx = double(x1) - double(x0);
  const double dy = double(y1) - double(y0);
  const double dist = std::sqrt(dx * dx + dy * dy);
  const double diam(r << 1);
  const double div = dist / diam;
  double div_int = 0.0;
  const double div_frac = std::modf(div, &div_int);
  unsigned int hops(div_int);
  if (div_frac != 0.0) {
    ++hops;
  }
  std::printf("%u\n", hops);
}
