ex3_20b.cpp

#include <iostream>
#include <vector>

using std::vector;
using std::cout;
using std::endl;
using std::cin;

int main()
{
    vector<int> ivec;
    for (int i; cin >> i; ivec.push_back(i));

    if (ivec.empty())
    {
        cout << "input at least one integer." << endl;
        return -1;
    }

    auto size = ivec.size();
    if (size % 2 != 0) size = size / 2 + 1;
    else size /= 2;

    for (int i = 0; i != size; ++i)
        cout << ivec[i] + ivec[ivec.size() - i - 1] << " ";
    cout << endl;

    return 0;
}