#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cmath>
const int maxn=1e3;
using namespace std;
int main()
{
	int b,c,t,n,m;
	int a[maxn];
	while(cin>>n&&n!=0)
	{
		int flag=1,sum=0;
		for(int i=0;i<n;++i)
		{
			cin>>a[i];
			if(a[i]<2) flag=0;
			sum+=a[i];
		}
		sort(a,a+n);
		if(flag==0) printf("-1\n");
		else printf("%d\n",sum-a[0]+2);
	}
}