n = int(input());
A = list(map(int, input().split()));
res = -1;
sum = 0;
for q in range(n):
    if A[q] <= sum + 1:
        sum = sum + A[q];
    else:
        res = sum + 1;
        break;
if res == -1:
    res = sum + 1;
print(res);