#include <bits/stdc++.h>
int r, x1, Y1, x2, Y2;
int main() {
  scanf("%d %d %d %d %d", &r, &x1, &Y1, &x2, &Y2);
  double dist = sqrt((double)(x1 - x2) * (x1 - x2) + (Y1 - Y2) * (Y1 - Y2));
  printf("%d", (int)ceil(dist / (2 * r)));
  return 0;
}
