process carry
for ( let i = n - 2 ; i >= 0 ; i -- ) { if ( c [ i ] == ' ' ) c [ i ] = ' ' ; else { let t = c [ i ] . charCodeAt ( ) - ' ' . charCodeAt ( ) + 1 ; c [ i ] = String . fromCharCode ( 48 + t ) ; break ; } } } let s1 = c . join ( " " ) ; if ( s1 [ 0 ] == ' ' ) s1 = " " + s1 ;