#include <stdio.h>
#include <stdlib.h>

#define POS "possible"
#define IMP "impossible"

void iniUse(char n,char use[]);
char searchSum(char n,char w[],char use[],short sum,short tmpS);

int compare(const void *a, const void *b)
{
	return *(char *)a - *(char *)b;
}

int main(void)
{
	char n,i;
	char *w,*use;
	char ret;
	short sum;

	scanf("%hhd",&n);
	w = (char *)malloc(sizeof(char) * n);
	sum = 0;
	for (i=0;i<n;i++) {
		scanf("%hhd",&w[i]);
		sum += w[i];
	}
	
	// check even
	if (sum % 2 == 1) {
		printf("%s\n",IMP);
		return 0;
	}

	sum /= 2;

	// sort to ascending
	qsort(w,n,sizeof(char),compare);

	// check large
	if (w[n-1] > sum) {
		printf("%s\n",IMP);
		return 0;
	}

	// search
	use = (char *)malloc(sizeof(char) * n);
	iniUse(n,use);
	ret = searchSum(n,w,use,sum,0);

	if (ret == 1) {
		printf("%s\n",POS);
	} else printf("%s\n",IMP);

	return 0;
}

void iniUse(char n,char use[])
{
	char i;
	for (i=0;i<n;i++) use[i] = 0;
	return;
}

char searchSum(char n,char w[],char use[],short sum,short tmpS)
{
	char i;
	char ret;
	short tmp;

/*
	printf("use= ");
	for (i=0;i<n;i++) printf("%hhd ",use[i]);
	printf("\n");
*/
	for (i=n-1;i>=0;i--) {
		if (use[i] == 1) continue;

		tmp = tmpS + w[i];
		if (tmp > sum) continue;
		use[i] = 1;
		if (tmp == sum) return 1;

		ret = searchSum(n,w,use,sum,tmp);
		if (ret == 1) return 1;
		use[i] = 0;
	}

	return 0;
}