Alaska

The Alaska Highway is a 1422-mile road connecting Dawson Creek and Delta Junction.

Sanggeun wants to drive his electric car from Dawson Creek to Delta Junction and then back to Dawson Creek. On a single full charge the car can travel 200 miles. There is a charging station at Dawson Creek, and there are more stations along the highway. Given the positions of the charging stations, write a program that determines whether Sanggeun can complete this round trip.

The input consists of several test cases. The first line of each test case contains the number of charging stations on the highway, $n$, a positive integer; the station at Dawson Creek is counted in $n$. Each of the next $n$ lines gives the position of one charging station, as its distance from Dawson Creek, which is at least 0 and at most 1422. No two charging stations are at the same position. The last line of the input contains 0, marking the end of the input.

For each test case, print POSSIBLE on its own line if Sanggeun can drive from Dawson Creek to Delta Junction and back to Dawson Creek, and IMPOSSIBLE otherwise.