这是昨天NMOS考试第15题，此题版权属于NUS High。
2020 students stand in a circle, each carrying a number 1, 2, ..., 2020 respectively in the clockwise direction. The counting starts from the first student (No. 1) and proceeds as A, B, C, D, E, A, B, C, D, E, ... around the circle clockwise. Students who are counted with E will stay and every other letter will leave the circle. For example, student No. 1, 2, 3, and 4 will leave the circle and student No. 5 stays. The remaining students form a smaller circle. If this counting continues along the subsequent circles, what is the number of the last student who stays in the smallest circle?
问题中最后一句的"last"是ID最大，还是按照A, B, C, D, E的顺序最后一个被叫到的意思呢？