//poj 1154
//sep9
#include 
  
   
using namespace std;
const int maxR=32;
char a[maxR][maxR];
int r,s;
int ans=1;
int vis[200];
void dfs(int i,int j,int len)
{
	ans=max(ans,len+1);
	if(i+1
   
    =0&&vis[a[i-1][j]]==0){ vis[a[i-1][j]]=1; dfs(i-1,j,len+1); vis[a[i-1][j]]=0; } if(j+1
    
     =0&&vis[a[i][j-1]]==0){ vis[a[i][j-1]]=1; dfs(i,j-1,len+1); vis[a[i][j-1]]=0; } } int main() { scanf("%d%d",&r,&s); for(int i=0;i