#include<bits/stdc++.h>
using namespace std;
int main()
{
int t;
cin>>t;
while(t--)
{
int n;
cin>>n;
string s;
cin>>s;
int ra=n;
int a=0,b=0,i=0,att=0;
while(i<2*n)
{
if(s[i]=='1')
a++;
if(s[i+1]=='1')
b++;
att=att+2;
if(abs(a-b)>(2*n-att)/2)
break;
i=i+2;
}
cout<<att<<endl;
}
}