#include<cstdio>
#include<math.h>
#include<iostream>
#include<algorithm>
using namespace std;
int main(){
		int n,a[520];
	while(scanf("%d",&n)!=EOF){
		if(n==0) break;
		int p=0;
		for(int i=0;i<n;i++){
			scanf("%d",&a[i]);
			if(a[i]==1){
			p=1;
			}
		}
		sort(a,a+n);
		int z=2;
		for(int i=n-1;i>0;i--){
			z+=a[i];
		} 
		if(p==0)
		printf("%d\n",z);
		else printf("-1\n");
	}
}