#include <bits/stdc++.h>
using namespace std;
double X0, Y0, X1, Y1, r;
int main() {
  scanf("%lf%lf%lf%lf%lf", &r, &X0, &Y0, &X1, &Y1);
  double count = sqrt(1.0 * ((X1 - X0) * (X1 - X0) + (Y1 - Y0) * (Y1 - Y0)));
  count = count / (2 * r);
  if (count > (long long)count)
    printf("%.0lf", count + 1);
  else
    printf("%.0lf", count);
}
