http://code.google.com/codejam/contest/dashboard?c=1128486#s=p0

#include<iostream>
char ch[51][51];
using namespace std;
int main()
{
    int t;
    int n , m , k=0 ;
    int i,j;
    cin>>t;
    while(t--)
    {
        cin>>n>>m;
        
        for(i=0;i<n; i++) cin>>ch[i];
        
        int j   , i  , sign = 0 ;
        int ans=0;
        for(  i = 0  ;  i < n  ; i++ )
        {
          for( j  =  0  ;  j  <  m  ;  j++  )
          {
              if( ch[i][j]!='/' && ch[i][j]!='\\' && ch[i][j]!='.' )
              {
                 if(ch[i][j+1]=='#' && ch[i+1][j]=='#' && ch[i+1][j+1]=='#')  
                 {
                     ch[i][j]='/';
                     ch[i+1][j]='\\';
                     ch[i][j+1]='\\';
                     ch[i+1][j+1]='/';
                     
                 }
                 else  { sign=1; break;}
                 
              }
          }
          if(sign==1) break;
        }
        for(i=0;i<n;i++)
        {
            for(j=0;j<m;j++)
                if(ch[i][j] == '#'){ ans=1;  break;}
            
        }
        cout<<"Case #"<<++k<<":"<<endl;
        
        if(ans==1) cout<<"Impossible"<<endl;
        else
        {
            for(i=0;i<n;i++)
              cout<<ch[i]<<endl;
        }
        
    }
    return 0;
}