Error reading dataset in R

I have problem in reading a dataset

My code :

require(igraph)
g <- graph(c(0, 1, 1, 2, 2, 0, 1, 3, 3, 4, 
               4, 5, 5, 3, 4, 6, 6, 7, 7, 8, 
               8, 6, 9, 10, 10, 11, 11, 9))

Error :

Error in graph(c(0, 1, 1, 2, 2, 0, 1, 3, 3, 4, 4, 5, 5, 3, 4, 6, 6, 7,  : 
  At structure_generators.c:84 : Invalid (negative) vertex id, Invalid vertex id