#include <iostream>
#include <vector>
 
using namespace std;
 
vector<int> performOps(vector<int> A) {
    vector<int> B(2 * A.size(), 0);
    for (int i = 0; i < A.size(); i++) {
        B[i] = A[i];
        B[i + A.size()] = A[(A.size() - i) % A.size()];
    }
    return B;
}
 
int main() {
	// your code goes here
	int arr[] = {5,10,2,1};
	vector<int> A(arr,arr+4);
	vector<int> B = performOps(A);
	for (int i = 0; i < B.size(); i++) {
	 cout<<B[i]<<" ";
	}
	return 0;
}

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