/* Sorts int array a[0..n-1] */
void mymergesort(int a[], int n);

/* Sorts int array a[low..hi] using the int array buffer[low..hi] */ 
void div_merge(int a[], int buffer[], int low, int hi);

/* Merges a[low..mid] and a[mid+1..hi] into b[low..hi] */
void merge(int a[], int b[], int low, int mid, int hi);