#include <iostream>
#include <cmath>
 
using namespace std;
typedef unsigned long long int ul;
 
void reset(int grades[6]){
    for(int i=0;i<6;i++)
        grades[i]=0;
}
 
ul average(int grades[6], int k,int n){
    ul res=0;
    for(int i=0;i<6;i++)
        res+=(ul)grades[i]*(ul)pow(i+1,k);
    return res/n;
}
int bestAverage(int grades[6],int n){
    int k=1;
    bool underFour = false, aboveFour = false;
    for(int i=0;i<6;i++){
        if (i<3 && grades[i]>0)
            underFour = true;
        if (i>3 && grades[i]>0)
            aboveFour = true;
    }
    if (underFour == true && aboveFour == false)
        return -1;
    else {
        while (average(grades,k,n)<(ul)pow(4,k)){
            k++;
        }
        return k;
    }
}
int main()
{
    int grades[6],t,n,number;
    cin>>t;
    for(int i=0;i<t;i++){
        reset(grades);
        cin>>n;
        if (n!=0){
            for(int j=0;j<n;j++){
                cin>>number;
                grades[number-1]++;
            }
            cout<<bestAverage(grades,n)<<endl;
        } else
            cout<<-1<<endl;
    }
    return 0;
}
 

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6
5
1 2 3 1 3
4
1 2 3 5
5
1 1 5 1 1
2
4 2
7
4 4 4 3 1 3 1
18
3 2 2 5 5 2 3 1 3 5 4 1 3 6 5 6 1 3