#!/usr/bin/gawk -fBEGIN{RS="[a-z]"# START PART 1COUNT=4# END PART 1 START PART 2COUNT=14# END PART 2}NR>COUNT{for(i=2;i<=length(a);i++)a[i-1]=a[i]deletea[length(a)]}{a[(NR==1?0:length(a))+1]=RT}NR>COUNT{for(iina){if(_a[a[i]]++==1){delete_anext}}printNRexit}