diff --git a/sorting-algorithms/merge_sort_recursive.py b/sorting-algorithms/merge_sort_recursive.py
index 49eb0a4..b5e3263 100644
--- a/sorting-algorithms/merge_sort_recursive.py
+++ b/sorting-algorithms/merge_sort_recursive.py
@@ -2,61 +2,65 @@
 
 # lst[low1]...lst[up1] and lst[low2]...lst[up2] merged to temp[low1]...temp[up2]
 def merge(lst, temp, low1, up1, low2, up2):
-	i = low1
-	j = low2
-	k = low1
-
-	while i<=up1 and j<=up2:
-		if lst[i] < lst[j]:
-			temp[k] = lst[i]
-			i += 1
-		else:
-			temp[k] = lst[j]
-			j += 1
-		k += 1
-
-	while i <= up1:
-		temp[k] = lst[i]
-		k += 1
-		i += 1
-	
-	while(j <= up2):
-		temp[k] = lst[j]
-		k += 1
-		j += 1
+    i = low1
+    j = low2
+    k = low1
+
+    while i <= up1 and j <= up2:
+        if lst[i] <= lst[j]:
+            temp[k] = lst[i]
+            i += 1
+        else:
+            temp[k] = lst[j]
+            j += 1
+        k += 1
+
+    while i <= up1:
+        temp[k] = lst[i]
+        k += 1
+        i += 1
+
+    while j <= up2:
+        temp[k] = lst[j]
+        k += 1
+        j += 1
+
 
 def copy(lst, temp, low, up):
-	i = low
-	while i<=up:
-		lst[i] = temp[i]
-		i += 1
+    i = low
+    while i <= up:
+        lst[i] = temp[i]
+        i += 1
 
-def merge_sort1(lst, low, up):
-	temp = [None]*(len(lst))
 
-	if low == up:	# if only one element
-		return
-	
-	mid = (low+up)//2
-	merge_sort1(lst,low,mid)	# Sort lst[low]....lst[mid]
-	merge_sort1(lst,mid+1,up)	# Sort lst[mid+1]....lst[up]
+def merge_sort1(lst, temp, low, up):
+    if low >= up:  # if only one element
+        return
 
-	# Merge lst[low]...lst[mid] and lst[mid+1]...lst[up] to temp[low]...temp[up]
-	merge(lst,temp,low,mid,mid+1,up)
+    mid = (low + up) // 2
+
+    merge_sort1(lst, temp, low, mid)        # Sort lst[low]....lst[mid]
+    merge_sort1(lst, temp, mid + 1, up)    # Sort lst[mid+1]....lst[up]
+
+    # Merge lst[low]...lst[mid] and lst[mid+1]...lst[up] to temp[low]...temp[up]
+    merge(lst, temp, low, mid, mid + 1, up)
+
+    # Copy temp[low]...temp[up] to lst[low]...lst[up]
+    copy(lst, temp, low, up)
 
-	# Copy temp[low]...temp[up] to lst[low]...lst[up]
-	copy(lst,temp,low,up)
 
 def merge_sort(lst, n):
-	merge_sort1(lst,0,n-1)
+    temp = [None] * n
+    merge_sort1(lst, temp, 0, n - 1)
+
 
 if __name__ == '__main__':
-	data_list = [8, 5, 89, 30, 42, 92, 64, 4, 21, 56, 3]
+    data_list = [8, 5, 89, 30, 42, 92, 64, 4, 21, 56, 3]
 
-	print("Unsorted list is :")
-	print(data_list)
+    print("Unsorted list is :")
+    print(data_list)
 
-	merge_sort(data_list,len(data_list))
+    merge_sort(data_list, len(data_list))
 
-	print("Sorted list is :")
-	print(data_list)
+    print("Sorted list is :")
+    print(data_list)