compare and print starting($1) and ending($2) number in given input $1 using unix

compare and print starting($1) and ending($2) number in given input $1
using unix

i having input in a.txt file,
10000030 10000029 10000028 10000027 10000026 10000024 10000023 10000021
10000018 10000018 10000017 10000016 10000015 10000014 10000013 10000011
10000010 10000009 10000008 10000006 10000005 10000004 10000003 10000002
10000001
need output in b.txt
10000001,10000006,6 10000008,10000011,4 10000013,10000019,7
10000021,10000021,1 10000023,10000024,2 10000026,10000030,5
Help me solve this script.....