#include <bits/stdc++.h>
int main() {
  double r, x1, y1, x2, y2;
  scanf("%lf %lf %lf %lf %lf", &r, &x1, &y1, &x2, &y2);
  double step = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  double i;
  int count = 0;
  if (step == 0) {
    printf("0");
  } else {
    for (i = 2 * r; i <= 1000000000; i = i + 2 * r) {
      if (step - i <= 0) {
        count++;
        break;
      } else {
        count++;
      }
    }
    printf("%d", count);
  }
  return 0;
}
