procedure solve(first:string;spos_f,epos_f:integer;mid:string;spos_m,epos_m:integer);
var i,root_m:integer;
begin
if spos_f > epos_f then exit;
for i:=spos_m to epos_m do
if first[spos_f]=mid[i] then begin
root_m:=i;
break;
end;
solve(first,spos_f+1,spos_f+(root_m-spos_m),mid,spos_m,root_m-1);
solve(first,spos_f+(root_m-spos_m)+1,epos_f,mid,root_m+1,epos_m);
write(first[spos_f]);
end;

var first,mid:string;
len:integer;
begin
readln(len);
readln(first);
readln(mid);
solve(first,1,len,mid,1,len);
writeln;
end.

输入：7
ABDCEGF
BDAGECF
输出：DBGEFCA