Problem:
Score : 800 points

Problem Statement

The beauty of a sequence a of length n is defined as a_1 \oplus \cdots \oplus a_n, where \oplus denotes the bitwise exclusive or (XOR).

You are given a sequence A of length N.
Snuke will insert zero or more partitions in A to divide it into some number of non-empty contiguous subsequences.

There are 2^{N-1} possible ways to insert partitions.
How many of them divide A into sequences whose beauties are all equal? Find this count modulo 10^{9}+7.

Constraints

All values in input are integers.

1 \leq N \leq 5 \times 10^5

0 \leq A_i < 2^{20}

Input

Input is given from Standard Input in the following format:

N
A_1 A_2 \ldots A_{N}

Output

Print the answer.

Sample Input 1

3
1 2 3

Sample Output 1

3

Four ways of dividing A shown below satisfy the condition. The condition is not satisfied only if A is divided into (1),(2),(3).

(1,2,3)

(1),(2,3)

(1,2),(3)

Sample Input 2

3
1 2 2

Sample Output 2

1

Sample Input 3

32
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Sample Output 3

147483634

Find the count modulo 10^{9}+7.

Sample Input 4

24
1 2 5 3 3 6 1 1 8 8 0 3 3 4 6 6 4 0 7 2 5 4 6 2

Sample Output 4

292

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

#include <bits/stdc++.h>
#define ADD(a, b) a = (a + ll(b)) % mod
#define MUL(a, b) a = (a * ll(b)) % mod
#define MAX(a, b) a = max(a, b)
#define MIN(a, b) a = min(a, b)
#define rep(i, a, b) for(int i = int(a); i < int(b); i++)
#define rer(i, a, b) for(int i = int(a) - 1; i >= int(b); i--)
#define all(a) (a).begin(), (a).end()
#define sz(v) (int)(v).size()
#define pb push_back
#define sec second
#define fst first
#define debug(fmt, ...) Debug(__LINE__, ":", fmt, ##__VA_ARGS__)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<int, pi> ppi;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> mat;
typedef complex<double> comp;
void Debug() {cerr << '\n'; }
template<class FIRST, class... REST>void Debug(FIRST arg, REST... rest){
	cerr<<arg<<" ";Debug(rest...);}
template<class T>ostream& operator<<(ostream& out,const vector<T>& v) {
	out<<"[";if(!v.empty()){rep(i,0,sz(v)-1)out<<v[i]<<", ";out<<v.back();}out<<"]";return out;}
template<class S, class T>ostream& operator<<(ostream& out,const pair<S, T>& v){
	out<<"("<<v.first<<", "<<v.second<<")";return out;}
const int MAX_N = 300010;
const int MAX_V = 100010;
const double eps = 1e-6;
const ll mod = 1000000007;
const int inf = 1 << 30;
const ll linf = 1LL << 60;
const double PI = 3.14159265358979323846;
mt19937 rng; //use it by rng() % mod, shuffle(all(vec), rng)
///////////////////////////////////////////////////////////////////////////////////////////////////

ll fac[MAX_N], inv[MAX_N], fiv[MAX_N]; //fiv:inv(fac(i))

ll mod_pow(ll a, ll n) {
	if(n == 0) return 1;
	ll res = mod_pow(a, n / 2);
	if(n % 2 == 0) return res * res % mod;
	else return a * res % mod * res % mod;
}

ll invf(ll a) {
	return mod_pow(a, mod - 2);
}

void C_init(int n) {
	fac[0] = fac[1] = 1; inv[1] = 1;
	fiv[0] = fiv[1] = 1;
	rep(i, 2, n + 1) {
		fac[i] = fac[i - 1] * i % mod;
		inv[i] = mod - inv[mod % i] * (mod / i) % mod;
		fiv[i] = fiv[i - 1] * inv[i] % mod;
	}
}

ll C(int a, int b) { //assume a >= b
	if(a < b || a < 0 || b < 0) return 0;
	return fac[a] * fiv[b] % mod * fiv[a - b] % mod;
}

struct Ruiseki {
	int N;
	vector<ll> B;
	void init(int n) {
		N = n; B = vector<ll>(N + 1, 0);
	}
	Ruiseki() {}
	Ruiseki(int n) { init(n); }
	void add(int a, ll v) {
		if(a < 0 || N <= a) return;
		B[a + 1] += v;
	}
	void sweep() {
		rep(i, 1, N + 1) B[i] += B[i - 1];
	}
	ll get(int a, int b) { //[a, b)
		if(a >= b) return 0;
		a = max(a, 0); b = min(b, N);
		return B[b] - B[a];
	}
};


int N;
vector<int> G[1 << 20];
int A[MAX_N];
Ruiseki rui;

void solve() {
	cin >> N;
	ll ans = 0;
	C_init(N);
	rui.init(N);
	rep(i, 0, N) cin >> A[i];
	int sum = 0, cnt = 1;
	rep(i, 0, N) {
		sum ^= A[i];
		if(sum == 0) {
			rui.add(i, 1);
			// debug(i);
			cnt++;
		}
		else G[sum].pb(i);
	}
	rui.sweep();
	// debug(sum, cnt);
	if(sum == 0) {
		ADD(ans, mod_pow(2, cnt - 2));
	}
	rep(i, 1, (1 << 20)) {
		if(sz(G[i]) == 0) continue;
		ll suma = 0, sumz = 1;
		// debug(G[i]);
		rep(j, 0, sz(G[i])) {
			// debug(i, j, suma, sumz);
			ll v = sumz;
			ADD(suma, v);
			if(j != sz(G[i]) - 1) {
				ll c = rui.get(G[i][j], G[i][j + 1]);
				ADD(sumz, suma * c % mod);
				// debug(G[i][j], G[i][j + 1], c);
			}
		}
		if(sum == 0) {
			ADD(ans, suma);
		}
		else if(sum == i) {
			ADD(ans, sumz);
		}
	}
	cout << ans << "\n";
}

uint32_t rd() {
	uint32_t res;
#ifdef __MINGW32__
	asm volatile("rdrand %0" :"=a"(res) ::"cc");
#else
	res = std::random_device()();
#endif
	return res;
}

int main() {
#ifndef LOCAL
	ios::sync_with_stdio(false);
    cin.tie(0);
#endif
    cout << fixed;
	cout.precision(20);
    cerr << fixed;
	cerr.precision(6);
	rng.seed(rd());
#ifdef LOCAL
	//freopen("in.txt", "wt", stdout); //for tester
    freopen("in.txt", "rt", stdin);
#endif	
	solve();
    cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
	return 0;
}