uses crt;
type
  valtype=char;
  tsign=(none,addition,substraction,multiplication,division);
  pnode=^tnode;
  tnode=record
    l,r,next:pnode;
    val:valtype;
    sign:tsign;
  end;

function tostr(v:integer):string;
var s: string;
begin
  str(v,s);
  tostr:=s;
end;

function toval(s:string):word;
var v,c:word;
begin
  val(s,v,c);
  toval:=v;
end;

function nodebycount(root:pnode;number:word):pnode;
var
 p:word;
 a:pnode;
begin
  a:=root;
  for p:=1 to number-1 do a:=a^.next;
  nodebycount:=a;
end;

function createvaluenode(val:valtype):pnode;
var
 node:pnode;
begin
 new(node);
 node^.l:=nil;
 node^.r:=nil;
 node^.next:=nil;
 node^.sign:=none;
 node^.val:=val;;
 createvaluenode:=node;
end;
function createsignnode(l,r:pnode;sign:char):pnode;
var
 node:pnode;
begin
 new(node);
 node^.l:=l;
 node^.r:=r;
 node^.next:=nil;
 node^.val:=#0;
 case sign of
   '*': node^.sign:=multiplication;
   '/': node^.sign:=division;
   '+': node^.sign:=addition;
   '-': node^.sign:=substraction;
 end;
 createsignnode:=node;
end;

function maketree(var s:string;var root:pnode):pnode;
var
 p,o,i,j:byte;
 valch:byte;
 s2,s3:string;
 node,ln,rn:pnode;
begin
 s:='('+s+')';
 valch:=0;

 root:=nil;
 s2:='';
 for p:=1 to length(s) do
 begin
   if s[p] in ['A'..'Z'] then
   begin
     inc(valch);
     if root=nil then
     begin
       root:=createvaluenode(s[p]);
       node:=root;
     end else
     begin
       node^.next:=createvaluenode(s[p]);
       node:=node^.next;
     end;
     s2:=s2+tostr(valch);
   end else if s[p]<>' ' then s2:=s2+s[p];
 end;
 s:=s2;
 s2:='';
 for p:=1 to length(s) do if s[p]=')' then
 begin
   for o:=length(s2) downto 1 do if s2[o]='(' then break;
   s3:=copy(s2,o+1,255);
   s2:=copy(s2,1,o-1);
   o:=1;
   repeat
     if s3[o] in ['*','/'] then
     begin
       inc(valch);
       i:=1;
       while(o>1+i)and(s3[o-1-i] in ['0'..'9']) do inc(i);
       ln:=nodebycount(root,toval(copy(s3,o-i,i)));
       j:=1;
       while(o+j<length(s3))and(s3[o+1+j] in ['0'..'9'])do inc(j);
       rn:=nodebycount(root,toval(copy(s3,o+1,j)));
       node^.next:=createsignnode(ln,rn,s3[o]);
       node:=node^.next;
       dec(o,i);
       delete(s3,o,i+j+1);
       insert(tostr(valch),s3,o);
     end;
     inc(o);
   until o>length(s3);

   o:=1;
   repeat
     if s3[o] in ['+','-'] then
     begin
       inc(valch);
       i:=1;
       while(o>1+i)and(s3[o-1-i] in ['0'..'9']) do inc(i);
       ln:=nodebycount(root,toval(copy(s3,o-i,i)));
       j:=1;
       while(o+j<length(s3))and(s3[o+1+j] in ['0'..'9'])do inc(j);
       rn:=nodebycount(root,toval(copy(s3,o+1,j)));
       node^.next:=createsignnode(ln,rn,s3[o]);
       node:=node^.next;
       dec(o,i);
       delete(s3,o,i+j+1);
       insert(tostr(valch),s3,o);
     end;
     inc(o);
   until o>length(s3);
   s2:=s2+s3;
 end else s2:=s2+s[p];
 maketree:=nodebycount(root,valch);
end;

function makePrefix(node:pnode):string;
begin
 case node^.sign of
   multiplication: makePrefix:='*'+makePrefix(node^.l)+makePrefix(node^.r);
   division: makePrefix:='/'+makePrefix(node^.l)+makePrefix(node^.r);
   addition: makePrefix:='+'+makePrefix(node^.l)+makePrefix(node^.r);
   substraction: makePrefix:='-'+makePrefix(node^.l)+makePrefix(node^.r);
   none: makePrefix:=node^.val;
 end;
end;

const
  s: string='((A + B) * (C - D) + E) * F';

var
  root,node:pnode;

begin
  writeln('string = ', s);
  node:=maketree(s,root);
  writeln('prefix = ', makePrefix(node));
end.