class FTL:
    def __init__(self):
        self.lba_to_phys = {}
        self.phys_to_lba = {}

    def map(self, lba, phys):
        self.lba_to_phys[lba] = phys
        self.phys_to_lba[phys] = lba

    def get_phys(self, lba):
        return self.lba_to_phys.get(lba, None)

    def get_lba(self, phys):
        return self.phys_to_lba.get(phys, None)

    def invalidate(self, lba):
        phys = self.lba_to_phys.pop(lba, None)
        if phys:
            self.phys_to_lba.pop(phys, None)