#include <iostream>
 
using namespace std;
 
#define SIZE 14 //multiple of 3
void arrange(char arr[], int n, int i)
{
 
if(i == 1)
{
arr[1] = arr[n];
//arr[2] = arr[n <<1];
  return;
}
int a = arr[i - 1];
int b = arr[n + i - 1];
//int c = arr[2*n + i - 1];
 
arrange(arr, n, i - 1);
 
int x = 2* (i - 1);
arr[x] = a;
arr[x + 1] = b;
//arr[x + 2] = c;
}
 
int main()
{
int n = SIZE;
char a[]="a1b2c3d4";int i;
 
if(n != 0 && n % 2== 0)arrange(a, n/2, n/2);
for(i = 0; i <n;i++)
   cout << a[i] << " ";
 
 
}

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