If previous character is 2 then the words that can be formed are U ( 21 ) , V ( 22 ) , W ( 23 ) , X ( 24 ) Y ( 25 ) , Z ( 26 )
else if ( s [ i - 1 ] == ' ' ) dp [ i + 1 ] = ( dp [ i + 1 ] + 6 * dp [ i - 1 ] ) % M ;