#include <algorithm>
    #include <iostream>
    #include <iterator>
 
    int array[20] = {1,4,7,8,10,2,3,6,8,11,1,2,7,8,9,3,4,9,10,13};
 
    using namespace std;
 
    void MergeSort(int *arr, int start1, int start2, int start3, int start4, int size)
    {
       std::inplace_merge(arr + start1, arr + start2, arr + start3);
       std::inplace_merge(arr + start3, arr + start4, arr + size);
       std::inplace_merge(array, array + start3, arr + size);
    }
 
    int main()
    {
       MergeSort(array, 0, 5, 10, 15, 20);
       std::copy(array, array + 20, ostream_iterator<int>(cout, " "));
    }
 
 

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