#include <iostream>
using namespace std;
int main()
{
        setlocale(LC_ALL, "Russian");
        int *str;
        int n, j;
        cout << "Введите размер массива ";
        cin >> n;
        str = new int[n];
        for (int i = 0; i < n; i++)
        {
                cout << "Введите " << i + 1 << " элемент массива ";
                cin >> str[i];
        }
        for (int i = 3; i < n; i += 3)
        {
                cout << str[i] <<endl;
        }
        //system("pause");
}
 

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

NCAxIDIgMyA0

4 1 2 3 4