#include <iostream>

// you can use includes, for example:
// #include <algorithm>
#include <bitset>
#include <vector>
#include <limits>

constexpr size_t N_MAX_ELEMS = 1000000;

// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;

int solution(std::vector<int> A) {

    std::vector<uint64_t> ref(N_MAX_ELEMS/sizeof(uint64_t), 0);

    for (auto elem : A) {
        if (elem <= 0) {
            continue;
        }
        ref[elem/8] |= (1 << (elem%8));
    }

    for (size_t i = 0; i < ref.size(); i++) {
        if (ref[i] != std::numeric_limits<uint64_t>::max()) {
            for (size_t j = 0; j < sizeof(uint64_t); j++) {
                if (i == 0 && j == 0) {
                    continue;
                }
                if ((ref[i]&(1 << j))==0) {
                    return (i*8+j);
                }
            }
        }
    }

    return N_MAX_ELEMS+1;
}


int main() {
    std::cout << solution({1,3,4,5,1,6}) << std::endl;
    return 0;
}