#include <bits/stdc++.h>
int main() {
  double r, x, y, x1, y1;
  double d;
  scanf("%lf%lf%lf%lf%lf", &r, &x, &y, &x1, &y1);
  d = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  int i = 0;
  if (d == 0)
    printf("0");
  else {
    while (d - 2 * r > 0) {
      i++;
      d -= 2 * r;
    }
    printf("%d", i + 1);
  }
}
