# queue
function enq( d ){
	q[tail++] = d
}
function deq(){
	return q[head++]
}
function peek(){
	return q[head]
}
function qempty(){
	return head>=tail
}

# paths
function linkedto(path, d ){
	t = path
	gsub(d,"",t)
	gsub("-","",t)
	return t
}
function dests(arr,node){
	delete arr
	p=0
	for( i in path ){
		if(path[i]~node){
			arr[p++] = linkedto(path[i],node)
		}
	}
}

function hasduplicate( str ){ # true if lowercase duplicates
	split(str, arr, ",")
	for(i in arr){
		if( tolower(arr[i]) == arr[i]){
			for( j in arr ){
				if (i!=j && arr[i] == arr[j])
					return 1
			}
		}
	}
	return 0
}

{
	path[NR] = $0
}
END{
	s = "start"
	enq(s)

	do{
		if(peek()~"end"){
			stack[sp++] = deq() # done
		}
		else if(hasduplicate(peek())){
			deq()
		}
		else if(!qempty()){
			s=deq(); #print "deq:", s, head, tail
			split(s, arr, ",")
			nd = arr[length(arr)]
			dests(a, nd)
			for(i in a){
				enq( s "," a[i] )
#				print "enq:", s "," a[i]
			}
		}
	}while(!qempty())
#	for(i in stack) print stack[i]
	print sp
}