#include<iostream>
#include<cstring>
#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
const int N = 2e6+10, M = 2e2+11, inf = 2e9, mod = 1e9+7;

int p[N],a[N],n;
int manacher(int l)
{
    int mx = 0, id = 0;
    memset(p,0,sizeof(p));
    for(int i=1;i<l;i++)
    {
        if(p[id]+id>i)p[i]=min(p[2*id-i],p[id]+id-i);
        else p[i]=1;
        while(a[i-p[i]] == a[i+p[i]]&&a[i-p[i]] <= a[i-p[i]+2])++p[i];
        if(id+p[id]<i+p[i])id=i;
        if(mx<p[i])mx=p[i];
    }
    return mx-1;
}
int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&n);
        a[0]=-1;
        for(int i=1;i<=n;i++) {
            a[i*2-1]=0;
            scanf("%d",&a[i*2]);
        }
        a[2*n+1]=0;
        printf("%d\n",manacher(2*n+1));
    }
    return 0;
}