K-th element of two Arrays

'''
Read the docs of find median of two sorted array.
'''


from math import inf
class Solution:
    def kthElement(self, a, b, k):
        if len(a)>len(b):
            a,b=b,a
        n1=len(a)
        n2=len(b)

        l = max(0, k - n2)   # we take elements from the array1 in such a way that to get k-cut1 elements should be there in the arr2, It should not be there k-cut1 is gonna exceed the arr2 length
        r = min(k, n1)
        while l<=r:
            cut1= (l+r)//2
            cut2= k-cut1

            left_first= a[cut1-1] if cut1>0 else -inf
            left_second=b[cut2-1] if cut2>0 else -inf
            right_first=a[cut1] if cut1<n1 else inf
            right_second=b[cut2] if cut2<n2 else inf

            if left_first<=right_second and left_second<=right_first:
                return max(left_first,left_second)

            elif left_first>right_second:
                r=cut1-1
            else:
                l=cut1+1
        return -1