#include <stdio.h>

int x = 0;

void search(int left, int right, int sum, int sum2, int *a)
{
	if(x) return;
	int i;
	for( i = left; i < right; i++){
		if( sum == sum2 + a[i])x = 1;
		if( sum > sum2 + a[i]) {
			search(i+1, right, sum, sum2 + a[i], a);
		}
	}
}

int main(void)
{
	int n, a[101], i, sum = 0;
	scanf("%d", &n);
	for( i = 0; i < n; i++) {
		scanf("%d", &a[i]);
		sum += a[i];
	}
	if( sum%2 ) {
		printf("impossible\n");
		return 0;
	}

	search(0, n-1, sum/2, 0, a);
	(x)? printf("possible\n") : printf("impossible\n");

	return 0;
}