program prog;
var mutex,reader,writer:semaphore;
    lec,nee,nle,writing:integer;
process LECTOR;
    begin
        repeat
            wait(mutex);
            if (writing=1) or (nee>0) then
            begin
                nle:=nle+1;
                signal(mutex);
                wait(reader);
                nle:=nle-1;
            end;
            lec:=lec+1;
            if nle>0 then
                signal(reader)
            else
                signal(mutex);
            writeln('LEER RECURSO');
            wait(mutex);
            lec:=lec-1;
            if (lec=0) and (nee>0) then
                signal(writer)
            else
                signal(mutex);
        forever;
    end;
process ESCRITOR;
    begin
        repeat
            wait(mutex);
            if (writing=1) or (lec>0) then
            begin
                nee:=nee+1;
                signal(mutex);
                wait(writer);
                nee:=nee-1;
            end;
            writing:=1;
            signal(mutex);
            writeln('ESCRIBIR EN EL RECURSO');
            wait(mutex);
            writing:=0;
            if nee>0 then
                signal(writer)
            else begin
                if nle>0 then
                    signal(reader)
                else
                    signal(mutex);
            end;
        forever;
    end;

begin
    initial(mutex,1);
    initial(reader,1);
    initial(writer,1);
    lec:=0;
    nle:=0;
    nee:=0;
    writing:=0;
    cobegin
        LECTOR;
        ESCRITOR;
    coend;
end.