C++ Program for Mergesort

#include<iostream>
using namespace std;
int main()
{
        void mergesort(int[],int,int);
        int A[7]={1,2,5,3,7,6,4};
        int low=0,high=6;
        mergesort(A,0,6);
        for(int i=low;i<=high;i++)
        {
                cout<<A[i]<<" ";
        }
        cout<<endl;
        return 0;
}
void mergesort(int A[7],int low,int high)
{
        if(low==high)
        {
                return;
        }
        int mid=(low+high)/2;
        mergesort(A,low,mid);
        mergesort(A,mid+1,high);
        int a=low;
        int b=mid+1;
        int B[100],j=0;
        while(a<=mid && b<=high)
        {
                if(A[a]<A[b])
                {
                        B[j]=A[a];
                        j++;
                        a++;
                }
                else if(A[b]<A[a])
                {
                        B[j]=A[b];
                        j++;
                        b++;
                }
        }
        while(a<=mid)
        {
                B[j]=A[a];
                j++;
                a++;
        }
        while(b<=high)
        {
                B[j]=A[b];
                j++;
                b++;
        }
        int k=0;
        for(int i=low;i<=high;i++)
        {
                A[i]=B[k];
                k++;
        }
}