This is a really dumb question but I had unprotected sex and am gonna take a plan b pill within maybe 15-20 hours after having sex. I don’t want to be affected by the hormones too much so could I take half of the pill or do I need to take the whole pill to avoid pregnancy?

I know this question was dumb but please don’t be a smart ass and answer the question if I need to take the whole pill to be safe or will half work