#include <iostream>
#include <string>
#include <vector>
using namespace std;

int T;
int arr[1001001];
int nn,n,x;
vector<int> rgt;
vector<int> lft;


int sgt[1001001];

void inc(int l,int r){
	for(int i=l;i<=r;i++){
		sgt[i]++;
	}
}
void dec(int l,int r){
	for(int i=l;i<=r;i++){
		if(sgt[i] > 0)sgt[i]--;
	}
}

int cnt(int l,int r){
	int ret=0;
	for(int i=l;i<=r;i++){
		if(sgt[i] > 0)ret++;
	}
	return ret;
}
int main(){
    freopen("chairs.in","r",stdin);
	cin>>T;
	while(T--){
		cin>>nn;
		int prv= -2;
		n=0;
		int count =0;
		for(int i=0;i<nn;i++){
			cin>>x;
			count += x;
			if(x == 1){
				arr[n++] = i - prv -1;
				prv = i;
			}
		}
		if(count  > (nn+1)/2){
			cout<<-1<<endl;
			continue;
		}
		arr[n++] = nn - prv;
		for(int i=0;i<=n;i++){
			sgt[i]=0;
		}
		rgt.clear();
		lft.clear();
		for(int i=n-1;i>=0;i--){
			while(arr[i] > 1){
				rgt.push_back(i);
				arr[i]--;
			}
		}

		long long sol = 0;
		for(int i=0;i<n;i++){
			if(arr[i] != 0){
				while(rgt.size() >  0 && rgt.back() <= i){
					lft.push_back(rgt.back());
					rgt.pop_back();
				}
				continue;
			}
			bool take_left;
			if(rgt.size() == 0){
				take_left=true;
			} else if(lft.size() == 0){
				take_left=false;
			} else {
				int L_i = lft.back();
				int R_i = rgt.back();
				if(i - L_i  - 2*cnt(L_i,i-1)  <= R_i - i){
					take_left=true;
				} else {
					take_left=false;
				}
			}

			if(take_left){
				int L_i = lft.back();
				lft.pop_back();
				sol += i - L_i  - 2*cnt(L_i,i-1);
				dec(L_i,i-1);
			} else {
				int R_i = rgt.back();
				rgt.pop_back();
				sol += R_i - i;
				inc(i,R_i-1);
			}
		}
		cout<<sol<<endl;
	}
}