import operator


def sub_wo_carry(n1, n2):
    """
    Substract two integer strings of same length without carry
    >>> sub_wo_carry('9007', '1234')
    '8873'
    """
    l1 = [int(x)+10 for x in str(n1)]
    l2 = [int(x) for x in str(n2)] 
    res1 = map(operator.sub, l1, l2)
    res2 = [str(x)[-1] for x in res1]
    return "".join(res2)