1. An information processing apparatus comprising: upper nodes each including a plurality of weak classifiers that learns learning samples with a first label of a first range among learning samples classified with a plurality of labels; first lower nodes each including a plurality of weak classifiers that learns learning samples with a second label of a second range based on results of classification by the upper nodes, the second range being a part of the first range; and second lower nodes each including a plurality of weak classifiers that learns learning samples with a third label of a third range based on the results of classification by the upper nodes, the third range being a part of the first range and different from the second range.