蓝桥/16/B.5/装修报价

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#include<iostream>
#include<vector>
using namespace std;

using ll=long long;
const int P=1e9+7;
int n;

int main()
{
		ios::sync_with_stdio(0),cin.tie(0);
		cin>>n;
		vector<ll> x(n+1);
		for(int i=1;i<=n;i++){
			cin>>x[i];
			x[i]^=x[i-1];		
		}
		
		ll ans=x[n]%P;
		ll p=1;
		
		for(int i=n-1;i>=1;i--){
			ans=(ans+(2*x[i]%P*p%P))%P;
			p=p*3%P;
		}
		
		cout<<ans<<"\n";
		
		return 0;
}