algorithms – What is the smallest value of x for which this holds?

I’m learning I/O Efficient Algorithm on Coursera and struggling on the question:

Suppose we run an algorithm Alg on a machine with internal
memory size MM that uses the LRU replacement policy, and we compare
the number of I/Os that are performed to the number of I/Os when we
would run is on a machine with internal memory size M/3M/3 that uses MIN, the optimal replacement policy. Then we can say that

Alg(LRU,M)≤x⋅Alg(MIN,M/3).

What is the smallest value of xx for which this holds?