O <= n

#include <iostream>
#include <vector>

int main()
{
    std::vector<int> victor;
    int count = 0;
    std::cin >> count;
    victor.resize(count);
    for (int i = 0; i < count; ++i)
    {
        std::cin >> victor[i];
    }

    int max = 0;
    for (int i = 0; i < count && victor[i] <= max + 1; ++i)
    {
        max += victor[i];
    }
    std::cout << max + 1 << "\n";
    return 0;
}