#include <bits/stdc++.h>
using namespace std;
long long OO = 10e9;
long long int maxSubArraySum(long long int a[], long long int size) {
  long long int max_so_far = a[0], i;
  long long int curr_max = a[0];
  for (i = 1; i < size; i++) {
    curr_max = max(a[i], curr_max + a[i]);
    max_so_far = max(max_so_far, curr_max);
  }
  return max_so_far;
}
int main() {
  int r, x, y, x2, y2;
  cin >> r >> x >> y >> x2 >> y2;
  cout << ceil(sqrtl(pow((x - x2), 2) + pow((y - y2), 2)) / (2 * r)) << endl;
}
