Given the emotion sadness and the tweet "Africa has unique and tremendous problems with war, overpopulation, starvation and tribalism which makes moving Africa forward hard.", classify the intensity of the emotion displayed in the tweet. The classification options are: 0: no sadness can be inferred, 1: low amount of sadness can be inferred, 2: moderate amount of sadness can be inferred, 3: high amount of sadness can be inferred.