还是模拟，不过这也算是usaco中第一道不水的题，因为是2年前做的，觉得还挺难，现在也觉得好水了。。。
program beads;
var
c:char;
a:array[1..700] of char;
max,s,j,k,i,left,right,n:integer;
begin
assign(input,'beads.in');
reset(input);
assign(output,'beads.out');
rewrite(output);
readln(n);
for i:=1 to n do
read(a[i]);
left:=1;
right:=n;
for k:=0 to n-1 do
begin
s:=0;
c:=a[left];
inc(s);
i:=left;
if c<>'w' then
begin
while (a[i+1]=c) or (a[i+1]='w') do inc(i);
s:=s+(i-left);
end
else
begin
while a[i+1]=c do inc(i);
c:=a[i+1];
inc(i);
while (a[i+1]=c) or (a[i+1]='w') do inc(i);
s:=s+(i-left);
end;
c:=a[right];
inc(s);
j:=right;
if c<>'w' then
begin
while (a[j-1]=c) or (a[j-1]='w') do dec(j);
s:=s+(right-j);
end;
if s>n then
begin
writeln(n);
close(input);
close(output);
halt;
end;
if s>max then max:=s;
inc(right);
a[right]:=a[left];
inc(left);
end;
writeln(max);
close(input);
close(output);
end.
