Such a question is ripe. There is a graph. It is required to cover all the edges of the graph with the minimum number of cliques.

IMPORTANT: each edge is EXACTLY in one click.

Example: Graph edges: (1, 2), (1, 3), (2, 3), (3, 4), (2, 4). Output: 3.

I tried googling, but couldn't find anything.

Who can prove complexity class, I will be grateful!