#include<stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
#include<iostream>
#include<stdlib.h>
#include<map>
#include<queue>
#include<vector>
using namespace std;
int main()
{
	int n,a[550],ans=0,f,min;
	while(~scanf("%d",&n)){
		if(n==0) break;
		ans=0,f=1,min=600;
		for(int i=1;i<=n;i++){
			cin>>a[i];
			ans+=a[i];
			
			if(a[i]<min) min=a[i];
			
			if(a[i]<2){
				f=0;
			}
		} 
		if(f==1){
			printf("%d\n",ans-(min-2));
		}else{
			printf("-1\n");
		}
	}
}