liftover results usage: input bed file and output bed file have different rows, how can I link coordinates between input and output files?

Question

[wangjinpeng0225]

Hi, guys, I would like to convert the coordinates of a list of SNPs from BosTaurus 9 to BosTanrus 6 with liftover. The program produced two files: converted bed and unmapped bed. How can I know the relationship of each SNP between the input bed file and the output bed file.