try while true do let b=read_line()in let rec aux i=if i>=0then if b.[i]='0'then b.[i]<-'1'else(b.[i]<-'0';aux(i-1))in aux(String.length b-1);print_endline b done with _->()
Note that non-ascii characters in the above source code will be escaped (such as \x9f).