Program to perform Merge sort in python

"Program to perform Merge sort"
# Code for merge sort
def merge(a,b):
    c = []
    while len(a) != 0 and len(b) != 0:
        if a[0] < b[0]:
            c.append(a[0])
            a.remove(a[0])
        else:
            c.append(b[0])
            b.remove(b[0])
    if len(a) == 0:
        c += b
    else:
        c += a
    return c
 
   
# Code to split The List

def mergesort(x):
    if len(x) == 0 or len(x) == 1:
        return x
    else:
        middle = int(len(x)/2)
        a = mergesort(x[:middle])
        b = mergesort(x[middle:])
        return merge(a,b)
       
   
def main():
    List_size=int(input("Enter the Number of Elements : "))
    Slist=[]
    for i in range(0,List_size):
        print ("Enter the ", i ," item   ")
        E_item=int(input("The Value : "))
        Slist.append(E_item)
    print ("The Unsortede List")
    print (Slist)
    print ("The sorted List is")
    print (mergesort(Slist))
   
main()