3105: [cqoi2013]新Nim游戏

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<vector>
using namespace std;
#define rep(i,l,r) for(int i=l;i<=r;i++)
#define per(i,r,l) for(int i=r;i>=l;i--)
#define mmt(a,v) memset(a,v,sizeof(a))
typedef long long ll;
int a[105];
int base[40];
bool ins(int x){
per(i,30,0)
if((x>>i)&1){
if(!base[i]){
base[i]=x;
return true;
}else x^=base[i];
}
return !(!x);
}
int main(){
freopen("a.in","r",stdin);
int n;scanf("%d",&n);
ll ans=0,sum;
rep(i,1,n)scanf("%d",&a[i]),ans+=a[i];
sum=ans;
sort(a+1,a+1+n);
per(i,n,1)
if(ins(a[i]))ans-=a[i];
if(sum==ans)ans=-1;
printf("%lld\n",ans);
return 0;
}