# Lucky Seven

Discrete Mathematics Level pending

Let $$\mathbb{X}=\{1,2,3,...100\}$$ and $$\mathbb{Y}$$ be a non empty subset of $$\mathbb{X}$$ such that the sum of no two elements in $$\mathbb{Y}$$ is divisible by $$7$$. Find the maximum possible number of elements in $$\mathbb{Y}$$.

×