#include<iostream>#include<cstring>#include<cstdio>#include<algorithm>#include<cmath>#define INF 0x3f3f3f3fusing namespace std;int maxdp[100005][20],mindp[100005][20],lmax[100005],rmax[100005],a[100005],n;void rmq_init(int len){    for(int i = 1;i <= len;i++)    {        maxdp[i][0] = a[i];        mindp[i][0] = a[i];    }    for(int j = 1;(1<<j) <= len;j++)    {        for(int i = 1;i+(1<<j)-1 <= len;i++)        {            maxdp[i][j] = max(maxdp[i][j-1],maxdp[i+(1<<(j-1))][j-1]);            mindp[i][j] = min(mindp[i][j-1],mindp[i+(1<<(j-1))][j-1]);        }    }}int rmq_max(int l,int r){    int k = (int)(log((double)(r-l+1))/log(2.0));    return max(maxdp[l][k],maxdp[r-(1<<k)+1][k]);}int rmq_min(int l,int r){    int k = (int)(log((double)(r-l+1))/log(2.0));    return min(mindp[l][k],mindp[r-(1<<k)+1][k]);}int main(){    int T;    scanf("%d",&T);    while(T--)    {        scanf("%d",&n);        for(int i = 1;i <= n;i++)   scanf("%d",&a[i]);        rmq_init(n);        int tempmax = -INF,minnum = a[1],minpos = 1;        for(int i = 1;i < n;i++)        {            if(a[i] < minnum)            {                minnum = a[i];                minpos = i;            }            int temp = rmq_max(minpos+1,i+1)-minnum;            tempmax = max(temp,tempmax);            lmax[i+1] = tempmax;        }        tempmax = -INF;        int maxnum = a[n],maxpos = n;        for(int i = n;i > 1;i--)        {            if(a[i] > maxnum)            {                maxnum = a[i];                maxpos = i;            }            int temp = maxnum-rmq_min(i-1,maxpos-1);            tempmax = max(temp,tempmax);            rmax[i-1] = tempmax;        }        int ans = -INF;        for(int i = 2;i < n-2;i++)  ans = max(lmax[i]+rmax[i+1],ans);        printf("%d\n",ans);    }    return 0;}