open Printf open String let a=read_line()let n=length a;;printf"%s%c "a a.[0];for i=1to n-1do printf"%c%s%c "a.[n-i](make(n-1)' ')a.[i]done;printf"%c"a.[0];for i=1to n do printf"%c"a.[n-i]done
Note that non-ascii characters in the above source code will be escaped (such as \x9f).