It should always be possible by (rot13) hfvat whfg gur guerr zrgny-rqtrq pengrf.
1. Vs lbh chfu gjb pengrf gb gur evtug fvqr, gura gb gur gbc, gura yrsg, gur frpbaq pengr fubhyq or fgenvtug nobir gur ohggba. Chfu vg qbja.
2. Gura chfu gur erznvavat pengr hc gb jurer gur frpbaq jnf naq ntnva chfu vg qbja fb vg'yy or evtug orybj gur ohggba.
3. Gb trg n pengr bagb gur ohggba, lbh pna abj whfg chfu gur obggbz-zbfg pengr evtug, hc, naq qbja yvxr lbh'ir orra qbvat.