var i,max,sum:integer;
    s:string;
begin
  writeln('Enter sentence: ');
  readln(s);
  max:=0;
  sum:=0;
  for i:=1 to length(s) do
    begin
      if s[i]='a' then sum:=sum+1 else
        begin
          if sum<>max then
            begin
              max:=sum;
              sum:=0;
            end
        end
    end;
  if s[length(s)]='a' then
    if sum>max then max:=sum;
  writeln('Longest sequence: ', max);
end.