#include <bits/stdc++.h>
using namespace std;

#define all(x) (x).begin(),(x).end()
#define print(x) cout << (x) << '\n'
typedef long long ll;
using P = pair<int,int>;
using Graph = vector<vector<int>>;
const ll MOD = 1000000007;
//const ll MOD = 998244353;

template <typename T> inline bool chmax(T &a, T b) {return a < b ? a = b, true : false;}
template <typename T> inline bool chmin(T &a, T b) {return a > b ? a = b, true : false;}

void solve() {
    int n;  cin >> n;
    vector<ll> a(n);
    ll ans = 0;
    for(int i = 0; i < n; i++){
        cin >> a[i];
        ans ^= a[i];
    }
    for(int i = 0; i < 1 << (n - 1); i++){
        ll tx = 0;
        ll tmp = a[0];
        for(int j = 0; j < n - 1; j++){
            if(i & 1 << j){
                tmp |= a[j + 1];
            }else{
                tx ^= tmp;
                tmp = a[j + 1];
            }
        }
        tx ^= tmp;
        chmin(ans, tx);
    }
    print(ans);
}

int main() { 
    cin.tie(0); cout.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(18);

    int t;
    //cin >> t;
    t = 1;
    while(t--) solve();
    return 0;
}
#pragma GCC optimize "trapv"
#include<iostream>
#include <bits/stdc++.h>
using namespace std;
#define fio ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)
#define ll long long
#define ull unsigned long long
#define ui unsigned int
#define vi vector<int>
#define vll vector<ll>
#define pb push_back
#define ld long double
#define mp make_pair
#define pii pair<int,int>
#define mod 1000000007
#define rep(i,n) for(int i=0;i<n;i++)
#define repp(i,a,n) for(int i=a;i<n;i++)
#define all(v) v.begin(),v.end()
#define input(arr,n) for(ll i1=0;i1<n;i1++ )cin>>arr[i1]
vector<string> split(const string& s, char c) {
    vector<string> v; stringstream ss(s); string x;
    while (getline(ss, x, c)) v.push_back(x); return move(v);
}
template<typename T, typename... Args>
inline string arrStr(T arr, int n) {
    stringstream s; s << "[";
    for(int i = 0; i < n - 1; i++) s << arr[i] << ",";
    s << arr[n - 1] << "]";
    return s.str();
}
#define EVARS(args...) {__evars_begin(__LINE__); __evars(split(#args, ',').begin(), args);}
inline void __evars_begin(int line) { cerr << "#" << line << ": "; }
template<typename T> inline void __evars_out_var(vector<T> val) { cerr << arrStr(val, val.size()); }
template<typename T> inline void __evars_out_var(T* val) { cerr << arrStr(val, 10); }
template<typename T> inline void __evars_out_var(T val) { cerr << val; }
inline void __evars(vector<string>::iterator it) { cerr << endl; }
template<typename T, typename... Args>
inline void __evars(vector<string>::iterator it, T a, Args... args) {
    cerr << it->substr((*it)[0] == ' ', it->length()) << "=";
    __evars_out_var(a);
    cerr << "; ";
    __evars(++it, args...);
}
template<typename T_vector>
void output_vector(const T_vector &v, bool add_one = false, int start = -1, int end = -1) {
    if (start < 0) start = 0;
    if (end < 0) end = int(v.size());
 
    for (int i = start; i < end; i++)
        cout << v[i] + (add_one ? 1 : 0) << (i < end - 1 ? ' ' : '\n');
}
struct custom_hash {
    static uint64_t splitmix64(uint64_t x) {
        // http://xorshift.di.unimi.it/splitmix64.c
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};
template<class T, class H>using umap=unordered_map<T,H,custom_hash>;
template<class T>using uset=unordered_set<T,custom_hash>;
  map<char, char> near;
int main()
{
    #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    #endif
    fio;
    clock_t clk = clock();
    int t = 1;
    // cin >> t;
    while(t--)
    {
        long double n;
        cin >> n;
        long double ans = 0.0;
        for(int i = 1; i < n; i++)
        {
            ans += n / (n - i);
        }
        cout << fixed << setprecision(10);
        cout << ans << endl;
    }
    cerr << '\n'<<"Time (in s): " << double(clock() - clk) * 1.0 / CLOCKS_PER_SEC << '\n';    
}