MergeSort Implementatio

//C program to implement Merge Sort and count the basic number of steps executed.
//Author: Souvik Baruah

#include <stdio.h> 
int count[21]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};

void merge(int a[], int l, int m, int r) 
{ 
    int i, j, k, n1 = m - l + 1, n2 = r - m, L[n1], R[n2];      //Line 5
    count[4]+=1;

    for (i = 0; i < n1; i++) 
    {
        L[i] = a[l + i];      //Line 6
        count[5]+=1;
    }    
    for (j = 0; j < n2; j++)
    { 
        R[j] = a[m + 1 + j];  //Line 7
        count[6]+=1;
    } 
    i = 0;            //Line 8
    count[7]+=1;
    j = 0;            //Line 9
    count[8]+=1;
    k = l;            //Line 10
    count[9]+=1;
    while (i < n1 && j < n2) 
    { 
        if (L[i] <= R[j]) 
        { 
            a[k] = L[i];   //Line 11
            count[10]+=1;
            i++;           //Line 12
            count[11]+=1;
        } 
        else 
        { 
            a[k] = R[j];   //Line 13
            count[12]+=1;
            j++;           //Line 14
            count[13]+=1;
        } 
        k++;    //Line 15 
        count[14]+=1;
    } 

    while (i < n1) 
    { 
        a[k] = L[i];   //Line 16
        count[15]+=1;
        i++;           //Line 17
        count[16]+=1;
        k++;           //Line 18
        count[17]+=1;
    } 

    while (j < n2) 
    { 
        a[k] = R[j];   //Line 19
        count[18]+=1;
        j++;           //Line 20
        count[19]+=1;
        k++;           //Line 21
        count[20]+=1;
    } 
} 

void mergeSort(int a[], int l, int r) 
{ 
    if (l < r)
    { 
        int m = l + (r - l) / 2;      //Line 1
        count[0]+=1;
        mergeSort(a, l, m);           //Line 2
        count[1]+=1;
        mergeSort(a, m + 1, r);       //Line 3
        count[2]+=1;
        merge(a, l, m, r);            //Line 4
        count[3]+=1;
    } 
} 

void display(int a[], int n) 
{ 
	int i; 
    printf("The sorted array in ascending order is:\n");
	for (i = 0; i < n; i++) 
		printf("%d ", a[i]); 
	printf("\n"); 
    for(int i=0;i<21;i++)
    {
        printf("Line %d executed %d times\n",i+1,count[i]);
    }
} 

int main() 
{ 
	int n,i;
    int a[100]; 
	printf("Enter the number of elements:\n");
    scanf("%d",&n);
    a[n];
    printf("Enter the elements:\n");
    for(i=0;i<n;i++)
    {
        scanf("%d",&a[i]);
    }

	mergeSort(a,0,n-1); 
	display(a, n); 

	return 0; 
}