#include <cstdio>

// before
enum class Error {
    OK,
    NOT_FOUND,
};

Error find_even(const std::vector<int>& numbers,
                int& result)
{
    for (int n : numbers) {
        if (n % 2 == 0) {
            result = n;
            return Error::OK;
        }
    }
    return Error::NOT_FOUND;
}

int main(void)
{
    const std::vector<int> numbers = {1, 2, 3, 4};
    int result;
    if (find_even(numbers, result) == OK) {
        printf("result: %d\n", result);
    }
    return 0;
}
