#include<bits/stdc++.h>

using namespace std;

#define ll long long
#define all(a) a.begin(),a.end()
#define endl '\n'

bool palcheck(string &s,ll n)
{
    for(ll i=0;i<n/2;i++)
    {
        if(s[i]!=s[n-1-i])
        {
            return false;
        }
    }
    return true;
}

void solve()
{
    ll n;cin>>n;
    string s;
    cin>>s;
    if(!palcheck(s,n))cout<<n<<endl;
    else cout << 0<<endl;

}

int main()
{
    ios::sync_with_stdio(0); cin.tie(0);
    ll t;cin>>t;
    while(t--)
    {
      solve();
    }    
}