#include <bits/stdc++.h>

using namespace std;
//cambian de coprimo a sacar gcd neto
int GCD(int a,int b) {
	if(a%b==0) {
		return b;
	}else {
		return GCD(b,a%b);
	}

}

int main() {
	int T,count=0,gcdaux,N,num;
	vector<int> nums;
	cin>>T;
	while(count<T) {
		cin>>N;
		for(int i=0;i<N;i++) {
			cin>>num;
			nums.push_back(num);
		}
		gcdaux=nums.back();
		nums.pop_back();
		for(int i=0;i<N-1;i++) {
			gcdaux=GCD(gcdaux,nums[i]);
		}

		if(gcdaux==1) cout<<N<<endl;
		else cout<<"-1"<<endl;



		nums.clear();
		count++;
	}
	return 0;
}