N = int(input())
W = list(map(int, input().split()))

A = sum(W)

S = [[0]*(A+1)]*(N+1)
S[0][0] = 1

if (A/2).is_integer() == False:
    print('impossible')
    exit()
else:
    A = int(A/2)
    for i in range(N+1):
        for j in range(A+1):
            if S[i][j] == 1:
                if j + W[i] > A:
                    print('impossible')
                    exit()
                else:
                    S[i+1][j+W[i]] = 1
                    S[i+1][j] = 1
    if S[N][A] == 1:
        print('possible')
    else:
        print('impossible')