I am import a texonomy.csv like

x1, x2
x3,
, X4(Here there is no L1)
X5,X6
X7, , X8(Here there is no L2)
But Still it is creating taxonomy terms for X4 and X8
like shown below.
X1->X2
X3
X3->X4
X5->X6
X7->X8

I dont want that terms to create taxonomy.

Will any one please let me know how to Solve this