# -*- coding: utf-8 -*-
import sys

if __name__ == '__main__':
    N = int(input())
    weight_list = list(map(int, input().split()))
    weight_list.sort()
    if sum(weight_list) % 2 != 0:
        print('impossible')
        sys.exit()

    target_val = int(sum(weight_list) / 2)

    dp = [[0 for j in range(target_val + 1)] for i in range(len(weight_list))]
    for i in range(len(weight_list)):
        if i == 0:
            for j in range(target_val + 1):
                if weight_list[i] == j:
                    dp[i][j] = weight_list[i]
                    break
        else:
            for j in range(1, target_val + 1):
                if j - dp[i][j - 1] >= weight_list[i]:
                    dp[i][j] = max(dp[i - 1][j], dp[i][j - 1] + weight_list[i])
                    break
                else:
                    dp[i][j] = max(dp[i - 1][j], dp[i][j - 1])
        if dp[i][j] == target_val:
            print('possible')
            sys.exit()
    print('impossible')