you receive 5 point solve problemManao invent new operation string call fold each fold happen pair consecutive letter place second string run opposite direction align position fold use operation Manao convert string structure level fold operation perform See follow example claritywe denote position fold character for example word ABRACADABRA write ABRACADABRA indicate fold times leftmost pair b r letter second a D rightmost pair b r letter here example fold stringsABCDEFGHIJK ABCDEFGHIJK ABRACADABRA XXXXXXXXXXXXXX XXXXXX KJIHG KJIHGFEDCB AR X abcdef a DAB X acar xxxxx AB XOne example ABCDEFGHIJK KIJHGFEABCDManao notice fold string view pile letter for instance previous example pile read AHI BGJK CF DE Manao wonder high pile identical letter build fold operation give word note pile contain gap start level for example rightmost example pile consider valid gap start level