1. A system for generating a plurality of models for classifying input data into a plurality of classes on the basis of training data in which elements are previously classified into the plurality of classes, the system comprising: a sampling unit for sampling, from the training data, a plurality of datasets each including a predetermined number of elements classified into a minority class and a corresponding number of elements classified into a majority class, the corresponding number being determined in accordance with the predetermined number; and a learning unit for learning each of the plurality of models for classifying the input data into the plurality of classes, by using a machine learning technique on the basis of the plurality of sampled datasets.