Habitat Range of Fish

Marine researcher Sanggeun is studying $N$ species of fish that live in the East Sea.

The region where each species can live is an axis-aligned rectangular box (cuboid). A fish can move freely anywhere inside its habitat, including the boundary, but it never leaves that range.

A point in the sea is described by three numbers $(x, y, d)$: looking down from above, it is the point located $x$ to the east and $y$ to the north of a reference point, at depth $d$ below the sea surface. Assume the sea is a flat plane.

Write a program that computes the total volume of the region where at least $K$ species of fish can live.

The first line contains two integers $N$ and $K$. ($1 \le K \le N \le 50$)

Each of the next $N$ lines contains six integers $X_{i,1}\ Y_{i,1}\ D_{i,1}\ X_{i,2}\ Y_{i,2}\ D_{i,2}$ describing the habitat of one fish. ($0 \le X_{i,1} < X_{i,2} \le 10^6$, $0 \le Y_{i,1} < Y_{i,2} \le 10^6$, $0 \le D_{i,1} < D_{i,2} \le 10^6$)

The habitat of the $i$-th fish is the axis-aligned cuboid whose opposite corners are $(X_{i,1}, Y_{i,1}, D_{i,1})$ and $(X_{i,2}, Y_{i,2}, D_{i,2})$.

Print, on a single line, the integer volume of the region where at least $K$ species of fish can live.