#include<stdio.h>
int cmp(const void*a,const void*b){
	return *(int*)a-*(int*)b;
}
int check(int *w,int l,int s){
	if(s==0) return 1;
	if(s<w[0]) return 0;
	for(;l>=0;l--){
		if(check(w,l-1,s-w[l])) return 1;
	}
	return 0;
}
int main(){
	int i,n,w[128],s=0;
	scanf("%d",&n);
	for(i=0;i<n;i++){
		scanf("%d",&w[i]);
		s+=w[i];
	}
	qsort(w,n,sizeof(int),cmp);
	if(s%2==0){
		s/=2;
		if(check(w,n-2,s-w[n-1])) printf("possible\n");
		else printf("impossible\n");
	}else printf("impossible\n");
	return 0;
}