Merge Sort

# Merges two subarrays of arr[]. 
# First subarray is arr[l..m] 
# Second subarray is arr[m+1..r] 
def merge(arr, l, m, r): 
    n1 = m - l + 1
    n2 = r- m 
  
    # create temp arrays 
    L = [0] * (n1) 
    R = [0] * (n2) 
  
    # Copy data to temp arrays L[] and R[] 
    for i in range(0 , n1): 
        L[i] = arr[l + i] 
  
    for j in range(0 , n2): 
        R[j] = arr[m + 1 + j] 
  
    # Merge the temp arrays back into arr[l..r] 
    i = 0     # Initial index of first subarray 
    j = 0     # Initial index of second subarray 
    k = l     # Initial index of merged subarray 
  
    while i < n1 and j < n2 : 
        if L[i] <= R[j]: 
            arr[k] = L[i] 
            i += 1
        else: 
            arr[k] = R[j] 
            j += 1
        k += 1
  
    # Copy the remaining elements of L[], if there 
    # are any 
    while i < n1: 
        arr[k] = L[i] 
        i += 1
        k += 1
  
    # Copy the remaining elements of R[], if there 
    # are any 
    while j < n2: 
        arr[k] = R[j] 
        j += 1
        k += 1
  
# l is for left index and r is right index of the 
# sub-array of arr to be sorted 
def mergeSort(arr,l,r): 
    if l < r: 
  
        # Same as (l+r)//2, but avoids overflow for 
        # large l and h 
        m = (l+(r-1))//2
  
        # Sort first and second halves 
        mergeSort(arr, l, m) 
        mergeSort(arr, m+1, r) 
        merge(arr, l, m, r) 
		

#Get the elements from user
n = int(input("Enter the number of elements:"))
A=[]
print("Enter the elements:")
for i in range(n):
	A.append(int(input()))

mergeSort(A,0,len(A)-1)
print("Sorted Array:")
for i in range(n):
	print("At index",i,"the element is:",A[i])

Enter the number of elements:5
Enter the elements:
21
-1
-2
4
3
Sorted Array:
At index 0 the element is: -2
At index 1 the element is: -1
At index 2 the element is: 3
At index 3 the element is: 4
At index 4 the element is: 21