I 前缀和，二分，高性能优化 B站讲解https://www.bilibili.com/video/BV1GT4y1M78d?p=4

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double db;
typedef vector<int> vii;
typedef vector<ll> vll;
typedef pair<int,int> PII;
#define so sizeof
#define pb push_back
#define pf push_front
#define ppb pop_back
#define ppf pop_front
#define fi first
#define se second
#define mp make_pair
#define lb lower_bound
#define ub upper_bound
const db esp=1e-5;
const int N=2e5+10,M=1e7+10,Max=2e5,inf=0x3f3f3f3f,mod=998244353;
const ll INF=0x3f3f3f3f3f3f3f3f;

int n,m,a[N],ps[N],v,cnt;
struct VL{
    int v,len;
    VL(int v=0,int len=0):v(v),len(len){};
};
bool operator<(VL a,VL b){
    if(a.v!=b.v)
        return a.v<b.v;
    else return a.len<b.len;
}
VL vlen[M];
unordered_map<int,int> vis;

bool cmp0(VL a,VL b){
    return a.v<b.v;
}
void work(){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++) scanf("%d",&a[i]);
    for(int i=1;i<=n;i++) ps[i]=ps[i-1]^a[i];
    for(int l=1;l<=n;l++){//l
        for(int r=l;r<=n;r++){//r
            int v=ps[r]^ps[l-1], len=r-l+1;
            if(vis[v]==0) vis[v]=cnt, vlen[cnt]=VL(v, len), cnt++;
            else if(vlen[vis[v]].len > len) vlen[vis[v]].len=len;
        }
    }
    sort(vlen, vlen + cnt,cmp0);
    for(int i=cnt-2;i>=0;i--)
        if(vlen[i].len > vlen[i + 1].len)
            vlen[i].len=vlen[i + 1].len;
    while(m--){
        scanf("%d",&v);
        int pos= lb(vlen, vlen + cnt, VL(v, -inf)) - vlen;
        if(pos>=cnt) puts("-1");
        else printf("%d\n", vlen[pos].len);
    }

    return ;
}


int main(){
        work();
    return 0;
}