text: Traverse the string , S
code: for ( let i = N - 1 ; i >= 0 ; i -- ) { if ( l > j ) break ; if ( S [ i ] . charCodeAt ( ) >= ( ' ' . charCodeAt ( ) + Math . min ( N , 25 ) ) || M . has ( S [ i ] ) && M . get ( S [ i ] ) > 1 ) {