#include<stdio.h>
#include<string.h>
#include<math.h>
int main(){

	int a;
	while(scanf("%d",&a)&&a!=0){
		int k[100];
		int i,j,t,sum=0,flag=1,max=600;
		for(i=0;i<a;i++){
			scanf("%d",&k[i]);
			sum+=k[i];
			if(k[i]<2)
				flag=-1;
			if(max>k[i])
				max=k[i];
		}
	
	if(flag==-1)
		printf("%d\n",flag);
	else
		printf("%d\n",sum-max+2);
}
}