problem3 ........\a ........\.\f.m ........\.\g1.m ........\.\g2.m ........\b ........\.\f.m ........\.\g1.m ........\.\g2.m ........\c ........\.\f.m ........\.\g1.m ........\.\g2.m ........\.\g3.m ........\d ........\.\f.m ........\.\g1.m ........\.\g2.m ........\.\g3.m