ROME — Pope Francis has revealed in an interview published Sunday that shortly after being elected pontiff in 2013 he wrote a resignation letter in case medical problems impede him from carrying out his duties. The pontiff added that he presumes that the prelate currently in that Vatican No. 2 role, Cardinal Pietro Parolin, now has the written instruction. “I have already signed my renunciation,” Francis revealed, noting that he did so early in the papacy.