#include <iostream>
#include <vector>

int main()
{
    std::vector<int> numbers;
    numbers.push_back(5);
    numbers.push_back(1);
    numbers.push_back(6);
    numbers.push_back(7);
    numbers.push_back(1);
    numbers.push_back(2);

    int sum = 0, value;
    for (int i = 0; i < numbers.size(); ++i) {
        sum += numbers[i];
    }
    value = sum / 2;

    for (int i = 0; i < numbers.size(); ++i) {
        int a = numbers[i];
        for (int j = i + 1; j < numbers.size(); ++j) {
            if (a + numbers[j] == value)
                std::cout << "true" << std::endl;
        }
    }

    return 0;
}