#include <iostream>
 
using namespace std;
 
int mul(int * arr, int shift, int N)
{
    switch (N)
    {
        case 1:
            return arr[shift];
        break;
 
        case 2:
            return (arr[shift] * arr[shift + 1]);
        break;
 
        default:
            int M = N / 2;
            return (mul(arr, shift, M) * mul(arr, shift + M, N - M));
    }
}
 
int main()
{
	int array[] = {5, 4, 3, 2, 1};
 
	cout << mul(array, 0, 5) << endl;
 
	return 0;
}

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