program prog;
var writing:boolean;
    lec,nee:integer;
    mutex:semaphore;
process LECTOR;
    begin
        repeat
            wait(mutex);
            while (writing=true) or (nee>0) do
            begin
                signal(mutex);
                wait(mutex);
            end;
            lec:=lec+1;
            signal(mutex);
            writeln('LEER RECURSO');
            wait(mutex);
            lec:=lec-1;
            signal(mutex);
        forever;
    end;
process ESCRITOR;
    begin
        repeat
            wait(mutex);
            nee:=nee+1;
            while (writing=true) or (lec>0) do
            begin
                signal(mutex);
                wait(mutex);
            end;
            writing:=true;
            nee:=nee-1;
            signal(mutex);
            writeln('ESCRIBIR EN EL RECURSO');
            wait(mutex);
            writing:=false;
            signal(mutex);
        forever;
    end;
begin
    initial(mutex,1);
    writing:=false;
    lec:=0;
    nee:=0;
    cobegin
        LECTOR;
        ESCRITOR;
    coend;
end.