#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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