Table for P2 's journey from end to meeting cell
for ( int i = 1 ; i <= N ; i ++ ) for ( int j = M ; j >= 1 ; j -- ) P2E [ i , j ] = Math . Max ( P2E [ i - 1 , j ] , P2E [ i , j + 1 ] ) + A [ i - 1 , j - 1 ] ;