#include #include using namespace atcoder; using namespace std; using ll=long long; using ld=long double; ld pie=3.141592653589793; ll mod=998244353; ll mod2=1000000007; ld inf=10000999999999900; int main(){ ll t; cin >> t; vectorans; for (ll o = 0; o < t; o++) { ll n; cin >> n; string s; cin >> s; vectorten(n+100,1),ten2(n+100,1); for (ll i = 1; i < ten.size(); i++) { ten[i]=ten[i-1]*9649; ten[i]%=mod; ten2[i]=ten2[i-1]*9649; ten2[i]%=mod2; } vectorhs(n),hs2(n); hs[0]=s[0]-'a'; hs2[0]=s[0]-'a'; for (ll i = 1; i sa=suffix_array(s); vectorss(n); for (ll i = 0; i < n; i++) { ss[sa[i]]=i; } for (ll i = 1; i*2 < n; i++) { ll y=hs[i-1]; ll z=hs[i*2-1]; z+=mod-(hs[i-1]*ten[i])%mod; z%=mod; ll yy=hs2[i-1]; ll zz=hs2[i*2-1]; zz+=mod2-(hs2[i-1]*ten2[i])%mod2; zz%=mod2; if (y==z&&yy==zz&&ss[2*i]