def operations(lst, value):
    if len(lst) == 1:
        return value == lst[0]
    return operations(lst[:-1], value-lst[-1]) or \
           operations(lst[:-1], value+lst[-1])


def operations(lst, value):
    sums = [lst[0]]
    for n in lst[1:]:
        tmp = []
        for s in sums:
            tmp.append(s+n)
            tmp.append(s-n)
        sums = tmp
    return value in sums



print(operations([2, 3, 6, 10], -5))
print(operations([5, 4, 6, 3], 11))