#include <bits/stdc++.h>
int main() {
  long long r, x1, x2, y1, y2, c;
  double a, b, s;
  scanf("%lld %lld %lld %lld %lld", &r, &x1, &y1, &x2, &y2);
  s = sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
  a = s / (2 * r);
  c = (int)a;
  if (a - c > 0)
    printf("%d", c + 1);
  else
    printf("%d", c);
  return 0;
}
