for(int i=,id=,mx=;i<=n;i++)

     {

         for(p[i]=(i<=mx)?min(p[id*-i],mx-i):;a[i-p[i]]==a[i+p[i]+];p[i]++);

         if(p[i]+i>mx) id=i,mx=i+p[i];

     }

 #include <cstdio>

 #include <algorithm>

 #include <set>

 using namespace std;

 int n,u,v,ans,p[],q[],nex[],fir[];

 char a[];

 set<int> t;

 inline int min(int a,int b){return (a<b)?a:b;}

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

 bool cmp(int a,int b)

 {

     return (a-p[a])<(b-p[b]);

 }

 int main()

 {

     scanf("%d",&n);

     char ch=getchar();

     while(ch<'a' || ch>'z') ch=getchar();

     for(int i=;i<=n;ch=getchar())

         a[i++]=ch;

     for(int i=,id=,mx=;i<=n;i++)

     {

         for(p[i]=(i<=mx)?min(p[id*-i],mx-i):;a[i-p[i]]==a[i+p[i]+];p[i]++);

         if(p[i]+i>mx) id=i,mx=i+p[i];

     }

     for(int i=;i<=n;i++)q[i]=i;

     sort(q+,q+n+,cmp);

     int now=;

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

     {

         while(now<=n&&q[now]-p[q[now]]<=i)

         {

             t.insert(q[now]);

             now++;

         }

         set<int>::iterator tmp=t.upper_bound(i+p[i]/);

         if(tmp!=t.begin())

         {

             ans=max(ans,(*--tmp-i)*);

         }

     }

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

     return ;

 }