#include <bits/stdc++.h>
int abs(int a) {
  if (a < 0) return -a;
  return a;
}
int main() {
  int r, x, y, x1, y1;
  scanf("%d%d%d%d%d", &r, &x, &y, &x1, &y1);
  int xx = abs(x - x1);
  int yy = abs(y - y1);
  double ans = sqrt(xx * xx + yy * yy);
  int an = ceil(ans / (double)(2 * r));
  printf("%d", an);
}
