Suppose we are given two graphs g1 = (v, e1 ) and g2 = (v, e2 ) with the same set of vertices v = {1, 2, . . , n}. prove that is it np-hard to find the smallest subset s ⊆ v of vertices whose deletion leaves identical subgraphs g1 \ s = g2 \ s. for example, given the graphs below, the smallest subset has size 4