Issue with merge sort

I'm trying to run merge sort using python and recursion it is working fine for some cases not not working fine for most of the cases please correct me I tried and unable to find error in code.

def merge_sort(a,min,max):
    if max-min<2:
        return a[min:max]

    mid=(min+max)//2
    L=merge_sort(a,min,mid)
    R=merge_sort(a,mid,max)
    return(sort(L,R))

def sort(L,R):
    (c,m,n)=([],len(L),len(R))
    (i,j)=(0,0)
    while(i+jif i==m :
            c.append(R[j])
            j+=1
        elif  j==m :
            c.append(L[i])
            i+=1
        elif R[j]<=L[i]:
            c.append(R[j])
            j+=1
        elif L[i]1
    return c