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.", rate the intensity of sadness shown. The rating scale is: 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.