n = int(input())
a = [int(i) for i in input().split()]
#print(n,a)
log = []
if sum(a) % 2 == 1:
    print("impossible")
else:
    half = sum(a) / 2
    for i in range(n):
        l = len(log)
        if a[i] not in log:
            log.append(a[i])
        for j in range(l):
            b = a[i] + log[j]
            if b not in log:
                log.append(b)
        #print(i,log,half)
        if half in log:
            print("possible")
            break
        else:
            if i == (n-1):
                print("impossibleB")