#include <vector>
#include <algorithm>
#include <iostream>
 
using namespace std;
 
 
 
int main([[maybe_unused]] int argc,
         [[maybe_unused]] const char * argv[])
{
    vector<int> a{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20};
 
    for(int i = 0, j = 4; i < j; ++i, --j)  swap(a[i],a[j]);
    for(int i = 5, j = 19; i < j; ++i, --j) swap(a[i],a[j]);
    for(int i = 0, j = 19; i < j; ++i, --j) swap(a[i],a[j]);
 
    for(int i: a) cout << i << " ";
 
 
}
 

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