1 #include<cstdio>
2 #include<cstdlib>
3 #include<cmath>
4 #include<cstring>
5 #include<algorithm>
6 #include<iostream>
7 #include<vector>
8 #include<map>
9 #include<set>
10 #include<queue>
11 #include<string>
12 #define inf 1000000000
13 #define maxn 500+100
14 #define maxm 500+100
15 #define eps 1e-10
16 #define ll long long
17 #define pa pair<int,int>
18 #define for0(i,n) for(int i=0;i<=(n);i++)
19 #define for1(i,n) for(int i=1;i<=(n);i++)
20 #define for2(i,x,y) for(int i=(x);i<=(y);i++)
21 #define for3(i,x,y) for(int i=(x);i>=(y);i--)
22 #define mod 1000000007
23 using namespace std;
24 inline int read()
25 {
26 int x=0,f=1;char ch=getchar();
27 while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
28 while(ch>=‘0‘&&ch<=‘9‘){x=10*x+ch-‘0‘;ch=getchar();}
29 return x*f;
30 }
31 int n,ans=0,f[30][30],g[30][30];
32 int main()
33 {
34 freopen("input.txt","r",stdin);
35 freopen("output.txt","w",stdout);
36 n=read();
37 for1(i,n)
38 {
39 char ch=getchar();
40 while(ch>‘z‘||ch<‘a‘)ch=getchar();
41 int x=ch-‘a‘;
42 for0(j,25)
43 {
44 f[x][j]++;
45 f[j][x]--;
46 if(!g[j][x])g[j][x]=1;
47 if(g[j][x]==2){g[j][x]=1;f[j][x]++;}
48 if(f[j][x]<=-1){f[j][x]=-1;g[j][x]=2;}
49 if(g[j][x])ans=max(ans,f[j][x]);
50 if(g[x][j])ans=max(ans,f[x][j]);
51 }
52 }
53 printf("%d\n",ans);
54 return 0;
55 }
