def do_OP_SIZE(vm):
    """
    >>> import binascii
    >>> s = [b'abcdef']
    >>> do_OP_SIZE(s)
    >>> print(s == [b'abcdef', b''])
    True
    >>> s = [b'abcdef'*1000]
    >>> do_OP_SIZE(s)
    >>> print(binascii.hexlify(s[-1]) == b'7017')
    True
    """
    vm.push_int(len(vm[-1]))
