int a[100],n;

int c(const void*a,const void*b){return*(int*)b-*(int*)a;}
/*降順ソート*/

int v(int x,int y,int i){
int j;
for(j=i+1;j<n&&y>=0;j++){
if(a[j]==x)return 1;
if(a[j]<x)if(v(x-a[j],y,j))return 1;
y-=a[j];
}
return 0;
}

int main(){
int i,s=0;
scanf("%d",&n);
for(i=0;~scanf("%d",a+i);)s+=a[i++];
if(s%2){puts("impossible");return 0;}
qsort(a,n,4,c);
puts(v(s/2,s/2,-1)?"possible":"impossible");
return 0;
}