#include <bits/stdc++.h>
using namespace std;
#define int long long
int32_t main()
{
int t;
cin>>t;
while(t--){
int i,j,n;
cin>>n;
vector<int>a(n);
int maxi=-1;
for(i=0;i<n;i++){
cin>>a[i];
maxi=max(maxi,a[i]);
}
int c=1,ans=-1;
for(i=0;i<n;i++){
if(a[i]==maxi){
ans=i+1;
}
}
cout<<ans<<"\n";
}
}
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