#include <bits/stdc++.h>
using namespace std;
const double EPS = 1e-9;
const double PI = 2 * acos(0.0);
int CASE = 1;
int TEST;
template <class T>
long long int ceilling(T a) {
  return (long long int)(a + 1.0);
}
int main(void) {
  long long int a = 0, b = 0, c = 0, x = 0, y = 0, r = 0;
  long double n = 0;
  scanf("%lld %lld %lld %lld %lld", &r, &x, &y, &a, &b);
  n = (a - x) * (a - x) + (b - y) * (b - y);
  n = (long double)sqrt(n);
  n = n / (2 * r);
  printf("%lld\n", ceilling(n));
  return 0;
}
