for i in range(int(input())):
w=int(input())
e=input()
if '1' in e:
r=min(e.index('1'),e[::-1].index('1'))
print(2*(w-r))
else:
print(w)
#include<bits/stdc++.h>
using namespace std;
#define int long long
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int t;cin>>t;
while(t--){
int n;cin>>n;
string s;cin>>s;
int x=s.length();
if(s[0]=='1'|| s[x-1]=='1')cout<<2*n<<endl;
else{
int y=0;
for(int i=0;i<x-1;i++){
if(s[i]=='1')y++;
}
int ans=n+y;
for(int i=0;i<x;i++){
if(s[i]=='1')ans=max(ans,max(2*(i+1),2*(x-i)));
}
cout<<ans<<endl;
}
}
return 0;
}
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