nhớ dùng ngôn ngữ c++17 nhé

#include <iostream>

#include <vector>

using namespace std;

const vector<int> perfect_number = {6, 28, 496, 8128};

int main(){

    int n; cin >> n;

    for (int i = 0; i < 4; i++)

        if (perfect_number[i] <= n) cout << perfect_number[i] << ' ';

    return 0;

}