topo_1.txt

00:00:00:00:00:04 s3
00:00:00:00:00:02 s2
s1 s2
00:00:00:00:00:03 s3
00:00:00:00:00:01 s2
s2 00:00:00:00:00:02
s3 00:00:00:00:00:04
s2 s1
s3 00:00:00:00:00:03
s1 s3
s3 s1
s2 00:00:00:00:00:01