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

#define POS "possible"
#define IMP "impossible"
#define DEBUG 0

char searchDP(char n,char w[],short sum);
void iniUse(char n,char use[]);
char searchBF(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;
	if (DEBUG) printf("sum = %hd\n",sum);

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

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

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

	// search DP
	ret = searchDP(n,w,sum);

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

	return 0;
}

char searchDP(char n,char w[],short sum)
{
	short i,j;
	char *dp;
	dp = (char *)malloc(sizeof(char) * n * 100);
	dp[0] = 1;
	for (i=1;i<n*100;i++) {
		dp[i] = 0;
	}

	for (i=n;i>=0;i--) {
		if (DEBUG) printf("w[%hd] = %hhd\n",i,w[i]);
		for (j=n*100;j>=0;j--) {
			if (dp[j] == 1) {
				if (DEBUG) printf("j=%hd\n",j);
				if (j+w[i] == sum) return 1;

				dp[j+w[i]] = 1;
			}
		}
	}

	return 0;
}

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

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

	return 0;
}