 Alon et al.define a "nonrepetitive coloring" of a graph to be an assignment of colors to the edges of the graph, such that there does not exist any even-length simple path in the graph in which the colors of the edges in the first half of the path form the same sequence as the colors of the edges in the second half of the path.The Thue number of a graph is the minimum number of colors needed in any nonrepetitive coloring.