римская 2 строки

#include <iostream>
#include <string>

using namespace std;

int main()
{
    string str, result;
    cout<<"Enter string"<<endl;
    getline(cin,str);
    const int len = str.length();
    for (int i = 1; i<len; i += 2)
    {
        result += str[i];
    }
    for (int i = len % 2 ? len - 1 : len - 2; i >= 0; i -= 2)
    {
        result += str[i];
    }
    cout << result << endl;
    system("pause");
    return 0;
}