tjut 5883

#include<bits/stdc++.h>  
using namespace std;  
const int maxn = 1e5+7;  
int a[maxn];  
int degree[maxn];  
int main()  
{  
    int T;  
    scanf("%d",&T);  
    while(T--)  
    {  
        memset(degree,0,sizeof(degree));  
        int n,m;  
        scanf("%d%d",&n,&m);  
        for(int i = 1;i<=n;i++)  
            scanf("%d",&a[i]);  
        for(int i = 1;i<=m;i++)  
        {  
            int u,v;  
            scanf("%d%d",&u,&v);  
            degree[u]++;  
            degree[v]++;  
        }  
        int cnt = 0;  
        for(int i = 1;i<=n;i++)  
            if(degree[i]&1)  
                cnt++;  
        if(cnt!=0 && cnt!=2)  
        {  
            printf("Impossible\n");  
            continue;  
        }  
        if(cnt==0)  
        {  
            int ans = 0;  
            for(int i = 1;i<=n;i++)  
                ans = max(ans,ans^a[i]);  
            printf("%d\n",ans);  
        }  
        else  
        {  
            int ans = 0;  
            for(int i = 1;i<=n;i++)  
            {  
                degree[i]=(degree[i]+1)/2;  
                if(degree[i]&1)  
                    ans^=a[i];  
            }  
            printf("%d\n",ans);  
        }  
    }  
}