#include <bits/stdc++.h>
using namespace std;
long long modular_pow(long long base, long long exponent, int modulus) {
  long long result = 1;
  while (exponent > 0) {
    if (exponent % 2 == 1) result = (result * base) % modulus;
    exponent = exponent >> 1;
    base = (base * base) % modulus;
  }
  return result;
}
int main() {
  int r, x, y, x1, y1;
  double dist, l;
  int ans;
  cin >> r >> x >> y >> x1 >> y1;
  dist = sqrt((double)(pow(x1 - x, 2) + pow(y1 - y, 2)));
  l = (dist) / (2 * r);
  ans = ceil(l);
  cout << ans;
  return 0;
}
