#include<bits/stdc++.h>
using namespace std;
const int MAXN=312;
int t;
int a[MAXN];
bool taken[MAXN];
void solve()
{
int n;
cin>>n;
for(int i=1;i<=n;i++)cin>>a[i];
set<int>possible;
for(int lady=1;lady<=n;lady++)
{
memset(taken,0,sizeof(taken));
taken[a[1]]=1;
bool ok=1;
for(int j=1;j<lady;j++)
{
if(taken[j]==0&&a[j+1]!=j)
{
ok=0;break;
}
taken[a[j+1]]=1;
}
if(ok)possible.insert(lady);
}
if(possible.size()==1)
{
cout<<(*possible.begin())<<endl;
}
else
{
cout<<0<<endl;
}
}
int main()
{
cin>>t;
while(t--)solve();
return 0;
}
