#include <iostream>

 #include <cstdio>

 #include <string.h>

 #pragma warning ( disable : 4996 )

 using namespace std;

 inline int Max(int a,int b) { return a>b?a:b; }

 inline int Min(int a,int b) { return a>b?b:a; }

 const int inf = 0x3f3f3f3f;

 const int maxn = 1e5+1e4+;

 char str[maxn];

 char nstr[maxn<<];

 int maxlen[maxn<<];

 int len, plen, ans;

 void init()

 {

     memset( nstr, , sizeof(nstr) );

     memset( maxlen, , sizeof(maxlen) );

     len = strlen(str);

     nstr[] = '$'; nstr[] = '#';

     int j = ;

     for ( int i = ; i < len; i++ )

     {

         nstr[j++] = str[i];

         nstr[j++] = '#';

     }

     nstr[j] = '\0';

     plen = j;

 }

 void solve()

 {

     ans = -;

     int id, mx = ;

     for ( int i = ; i < plen; i++ )

     {

         if( i < mx )

             maxlen[i] = Min( maxlen[*id-i], mx-i );

         else

             maxlen[i] = ;

         while( nstr[i-maxlen[i]] == nstr[i+maxlen[i]] )

             maxlen[i]++;

         if ( mx < i + maxlen[i] )

         {

             id = i;

             mx = i + maxlen[i];

         }

         ans = Max(ans, maxlen[i]-);

     }

 }

 int main()

 {

     while ( ~scanf("%s", str) )

     {

         init();

         solve();

         printf( "%d\n", ans );

     }

     return ;

 }

 #include <iostream>

 #include <cstdio>

 #include <string.h>

 #pragma warning ( disable : 4996 )

 using namespace std;

 inline int Max(int a,int b) { return a>b?a:b; }

 inline int Min(int a,int b) { return a>b?b:a; }

 const int inf = 0x3f3f3f3f;

 const int maxn = 1e5+;

 int maxl[maxn<<];

 int str[maxn], nstr[maxn<<];

 int N, ans, plen;

 void init()

 {

     memset( maxl, , sizeof(maxl) );

     memset( nstr, , sizeof(nstr) );

     nstr[] = ; nstr[] = -;

     int j = ;

     for( int i = ; i < N; i++ )

         { nstr[j++] = str[i]; nstr[j++] = -; }

     nstr[j] = -;

     plen = j;

 }

 void solve()

 {

     ans = -;

     int id, mx = ;

     for ( int i = ; i < plen; i++ )

     {

         if(i < mx)

             maxl[i] = Min(maxl[*id-i], mx-i);

         else

             maxl[i] = ;

         while( nstr[i-maxl[i]]==nstr[i+maxl[i]] && nstr[i-maxl[i]]<=nstr[i-maxl[i]+] )

             maxl[i]++;

         if(mx < i + maxl[i])

             { id = i; mx = i + maxl[i]; }

         ans = Max(ans, maxl[i]-);

     }

 }

 int main()

 {

     int all; cin >> all;

     while (all--)

     {

         cin >> N;

         for( int i = ; i < N; i++ )

             scanf( "%d", &str[i] );

         init();

         solve();

         printf( "%d\n", ans );

     }

     return ;

 }