program exp2;
var n,jr,jw,jb:integer;
ch1:char;
ch:array[1..20]d char;
begin
readln(n);
for i:=1 to n do read(ch[i]):
jr:=1;jwz=n;jb:=n;:
while (jr<=jw)do
begin
if(ch[jw]='R')
then begin
ch1:=Ch[jr];Ch[jr]:=ch[jw];ch[jw]:=ch1:jr:=jr+13
end
else if ch[jw]='W'
then jw:=jw-1
else begin
ch1:=ch[jw];ch[jw]:=ch[jb];ch[jb]:=ch1;jw:=jw-1;jb:=jb-1;
end
end;
for i:=1 to n do write(ch[i]);
writeln;
end.
输入:10
RBRBWWRBBR
输出：RRRRWWBBBB