filter_array

def filter_array(a,b):
    res = []
    i = j = 0
    while i < len(a) :
        print(i,j)
        if a[i] < b[j]:
            res.append(a[i])
            i += 1
        elif a[i] == b[j]:
            i += 1
            if j < len(b) - 1:
                j += 1
        elif a[i] > b[j]:
            if j < len(b) - 1:
                j += 1
            else :
                res.append(a[i])
                i += 1
    return res

a = [10,11,15,16,18,19]
b = [1,2,3,15,15,15,17]

filter_array(a,b)