#include <bits/stdc++.h>
using namespace std;
const long long INF = 1e9 + 5;
const long long mod = 1e9 + 7;
const long long N = 2e5 + 314;
const long double pi = 3.1415926535897932384626433832795;
long long bp(long long pow, long long n) {
  long long d = 1;
  while (n) {
    if (n % 2 == 1) d = (d * pow) % mod;
    pow = (pow * pow) % mod;
    n /= 2;
  }
  return d;
}
void solve() {
  long long r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  long long d = (ceil)((double)sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y)));
  r *= 2;
  cout << (long long)ceil((double)d / r);
}
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long t = 1;
  while (t--) solve();
}
