def get_shortest_unique_substring(arr, string):
    i, j = 0, 0
    min_i, min_j = 0, len(string) + 1
    counter = 0
    characters = { k:0 for k in arr }
    while i < len(string) and j < len(string):
        curr = string[j]
        print(curr)
        if curr in characters:
            characters[curr] += 1
            if characters[curr] == 1:
                counter += 1
        if counter == len(arr):
            while counter == len(arr):
                old = min_j - min_i
                new = j - i
                if new < old:
                    min_i, min_j = i, j
#                    print("Substring %d - %d" %(min_i,min_j))
                curr = string[i]
                if curr in characters:
                    characters[curr] -= 1
                    if characters[curr] == 0:
                        counter -= 1
                i+=1
        j += 1
    if min_j == len(string) + 1:
        return ""
    return string[min_i:min_j+1]