[igraph] vcount() shows one more node than existing one ??

[shahab]

Hi,

More probably I am mistaking, but I loaded an edge list graph
(graph<-read.graph("graph.txt", format="edgelist",0, TRUE), with 7
nodes but vcount(..) shows me 8 (nodes).
The nodes in my graph are identified by a numeric number  1-7 (graph
is shown in below).

Any reason for this inconsistency? should I start numbering from zero?

here is graph:

1       2       
1       5       
2       4       
4       6       
5       7       
3       1

best,
/Shahab