Problem:
Score: 600 points

Problem Statement

We have N non-negative integers: A_1, A_2, ..., A_N.

Consider painting at least one and at most N-1 integers among them in red, and painting the rest in blue.

Let the beauty of the painting be the \mbox{XOR} of the integers painted in red, plus the \mbox{XOR} of the integers painted in blue.

Find the maximum possible beauty of the painting.

What is \mbox{XOR}?

The bitwise \mbox{XOR} x_1 \oplus x_2 \oplus \ldots \oplus x_n of n non-negative integers x_1, x_2, \ldots, x_n is defined as follows:

When x_1 \oplus x_2 \oplus \ldots \oplus x_n is written in base two, the digit in the 2^k's place (k \geq 0) is 1 if the number of integers among x_1, x_2, \ldots, x_n whose binary representations have 1 in the 2^k's place is odd, and 0 if that count is even.

For example, 3 \oplus 5 = 6.

Constraints

All values in input are integers.

2 \leq N \leq 10^5

0 \leq A_i < 2^{60}\ (1 \leq i \leq N)

Input

Input is given from Standard Input in the following format:

N
A_1 A_2 ... A_N

Output

Print the maximum possible beauty of the painting.

Sample Input 1

3
3 6 5

Sample Output 1

12

If we paint 3, 6, 5 in blue, red, blue, respectively, the beauty will be (6) + (3 \oplus 5) = 12.

There is no way to paint the integers resulting in greater beauty than 12, so the answer is 12.

Sample Input 2

4
23 36 66 65

Sample Output 2

188

Sample Input 3

20
1008288677408720767 539403903321871999 1044301017184589821 215886900497862655 504277496111605629 972104334925272829 792625803473366909 972333547668684797 467386965442856573 755861732751878143 1151846447448561405 467257771752201853 683930041385277311 432010719984459389 319104378117934975 611451291444233983 647509226592964607 251832107792119421 827811265410084479 864032478037725181

Sample Output 3

2012721721873704572

A_i and the answer may not fit into a 32-bit integer type.

Solution in C++14 (GCC 5.4.1) (judge verdict: Runtime Error)

#include <bits/stdc++.h>

using namespace std;

#define SZ(x) (int)(x.size())

using ll = long long;
#define int ll
using ld = long double;
using P = pair<int, int>;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using vll = vector<ll>;
using vvll = vector<vector<ll>>;
const double eps = 1e-10;
const int INF = 1000000000;
const ll LINF = 1ll<<50;

template<typename T>
void printv(const vector<T>& s) {
  for(int i=0;i<(int)(s.size());++i) {
    cout << s[i];
    if(i == (int)(s.size())-1) cout << endl;
    else cout << " ";
  }
}

const int MAX_ROW = 510; // to be set appropriately
const int MAX_COL = 60; // to be set appropriately
struct BitMatrix {
    int H, W;
    bitset<MAX_COL> val[MAX_ROW];
    BitMatrix(int m = 1, int n = 1) : H(m), W(n) {}
    inline bitset<MAX_COL>& operator [] (int i) {return val[i];}
};

ostream& operator << (ostream& s, BitMatrix A) {
    s << endl; 
    for (int i = 0; i < A.H; ++i) {
        for (int j = 0; j < A.W; ++j) {
            s << A[i][j] << ", ";
        }
        s << endl;
    }
    return s;
}

inline BitMatrix operator * (BitMatrix A, BitMatrix B) {
    BitMatrix R(A.H, B.W);
    BitMatrix tB(B.W, B.H);
    for (int i = 0; i < tB.H; ++i) for (int j = 0; j < tB.W; ++j) tB[i][j] = B[j][i];
    for (int i = 0; i < R.H; ++i) for (int j = 0; j < R.W; ++j) R[i][j] = ((A[i] & tB[j]).count() & 1);
    return R;
}

inline BitMatrix pow(BitMatrix A, long long n) {
    BitMatrix R(A.H, A.H);
    for (int i = 0; i < A.H; ++i) R[i][i] = 1;
    while (n > 0) {
        if (n & 1) R = R * A;
        A = A * A;
        n >>= 1;
    }
    return R;
}


/* int GaussJordan(BitMatrix &A, bool is_extended = false) {
    int rank = 0;
    for (int col = 0; col < A.W; ++col) {
        if (is_extended && col == A.W - 1) break;
        int pivot = -1;
        for (int row = rank; row < A.H; ++row) {
            if (A[row][col]) {
                pivot = row;
                break;
            }
        }
        if (pivot == -1) continue;
        swap(A.val[pivot], A.val[rank]);
        for (int row = 0; row < A.H; ++row) {
            if (row != rank && A[row][col]) A[row] ^= A[rank];
        }
        ++rank;
    }
    return rank;
} */

int GaussJordan(BitMatrix &A, bool is_extended = false) {
    vector<bool> used(A.H, 0);
    for (int col = 0; col < A.W; ++col) {
        if (is_extended && col == A.W - 1) break;
        int pivot = -1;
        for (int row = 0; row < A.H; ++row) {
            if (used[row]) continue;
            if (A[row][col]) {
                pivot = row;
                break;
            }
        }
        if (pivot == -1) continue;
        for (int row = 0; row < A.H; ++row) {
            if (row != pivot && A[row][col]) A[row] ^= A[pivot];
        }
        used[pivot] = true;
    }
    return 0;
}

int linear_equation(BitMatrix A, vector<int> b, vector<int> &res) {
    int m = A.H, n = A.W;
    BitMatrix M(m, n + 1);
    for (int i = 0; i < m; ++i) {
        for (int j = 0; j < n; ++j) M[i][j] = A[i][j];
        M[i][n] = b[i];
    }
    int rank = GaussJordan(M, true);

    // check if it has no solution
    for (int row = rank; row < m; ++row) if (M[row][n]) return -1;

    // answer
    res.assign(n, 0);
    for (int i = 0; i < rank; ++i) res[i] = M[i][n];
    return rank;
}


const int MOD = 998244353;
long long modpow(long long a, long long n, long long mod) {
    long long res = 1;
    while (n > 0) {
        if (n & 1) res = res * a % mod;
        a = a * a % mod;
        n >>= 1;
    }
    return res;
}

signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);

  int n; cin >> n;
  vll a(n);
  ll ans = 0;
  for(int i=0;i<n;++i) {
    cin >> a[i];
    ans ^= a[i];
  }
  //cout << ans << endl;
  //cout << bitset<60>(ans) << endl;

  for(int i=0;i<n;++i) {
    a[i] = a[i] & (((1ll<<60)-1) ^ ans);
  }

  BitMatrix A(n, 60);
  for(int i=0;i<n;++i) {
    string tmp = "";
    for(int j=0;j<60;++j) {
      tmp.push_back((char)((a[i]>>j)&1) + '0');
    }
    //cout << tmp << endl;
    A.val[i] = bitset<MAX_COL>(tmp);
  }
  //cout << A << endl;
  GaussJordan(A);
  //cout << A << endl;
  ll add = 0;
  for(int i=0;i<n;++i) {
    ll now = 0;
    for(int j=0;j<60;++j) {
      now += ((ll)A[i][j])<<(59-j);
    }
    //cout << now << endl;
    add ^= now;
  }
  //cout << add << endl;

  cout << ans + 2 * add << endl;

}