merge sort

#include<stdio.h>


int a[20],n, nl, nr,left[20],right[20];
void merge(int *l, int *r, int *x);
void mergesort(int *x, int v);


void main()
{
    int i;


    printf("Enter the number of the elements \n");
    scanf("%d", &n);
    printf("Enter the array elements \n");
    for(i=0; i<n; i++)
    scanf("%d", &a[i]);
    printf("The array before sorting: \n");
    for(i=0; i<n; i++)
    printf("%d \n", a[i]);


    mergesort(a,n);

    printf("The array after sorting: \n");
    for(i=0; i<n; i++)
    printf("%d \n", a[i]);

}


void merge(int *l, int *r, int *x)
{
    int i=0, j=0, k=0;
    while(i<nl && j<nr)
    {
        if(l[i]<=r[j])
        {
            x[k]=l[i];
            i++;
        }
        else
        {
            x[k]=r[j];
            j++;
        }
        k++;
    }
    while(i<nl)
    {
        x[k]=l[i];
        i++;
        k++;
    }
    while(j<nr)
    {
        x[k]=r[j];
        j++;
        k++;
    }
}

void mergesort(int *x, int v)
{
    int mid,i;
    if(n<2)
    return;
    mid=n/2;
    nl=mid;
    nr= n-mid;

    for(i=0; i<mid; i++)
    left[i]=x[i];


        for(i=mid; i<n; i++)
    right[i-mid]= x[i];

    mergesort(left, mid);
    mergesort(right,v-mid);
    merge(left, right, a);


}