Slice a list of integers into four slices and applies bidirection search to each slice

Question

I am trying to write a function namely fourslicebidirectionSearch() where I have to do as a title said. My problem is I can write each function on its own but I couldn't figure out how to apply bidirection to four sliced integers.

def BiDirectionSearch(key, ls):
    i = 0  # to count a number loop
    j = len(ls) - 1
    while i < j:
        if ls[i] == key or ls[j] == key:
            return True, i + 1
        i += 1
        j -= 1
    return False, i


def FourSliceSearch(key, ls):
    n = int(len(ls) / 4)
    s1 = ls[0:n]
    s2 = ls[n:2 * n]
    s3 = ls[2 * n:3 * n]
    s4 = ls[3 * n:]
    i1 = 0
    i2 = 0
    i3 = 0
    i4 = 0
    count = 0  # to count a number of loop

    for i in range(len(s1)):

        if s1[i1] == key or s2[i2] == key or s3[i3] == key or s4[i4] == key:
            count += 1
            return True, count

        i1 += 1
        i2 += 1
        i3 += 1
        i4 += 1
        count += 1
    return False, count

myNum2 =  [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]
key = 9

result, loopcount2 = BiDirectionSearch(key, myNum2)
result, loopcount3 = FourSliceSearch(key, myNum2)
if result:
    print(f'{key} is found in {myNum2}')
    print(f'For LienarSearch(), it takes {loopcount} loop(s) to find {key}.')
    print(f'For BiDirectionSearch(), it takes {loopcount2} loop(s) to find {key}.')
    print(f'For FourSliceSearch(), it takes {loopcount3} loop(s) to find {key}.')

else:
    print(f'{key} is not in {myNum2} and it takes {loopcount} loop(s)')