Find the value of a mod 11 for large value of a as per the derived formula
for ( let i = a . length - 1 ; i >= 0 ; i -- ) { a_mod_11 = ( a_mod_11 + w * ( a [ i ] . charCodeAt ( 0 ) - ' ' . charCodeAt ( 0 ) ) ) % 11 ; w = w * - 1 ; }