  We prove that an inclusion-exclusion inspired expression of Schubert
polynomials of permutations that avoid the patterns 1432 and 1423 is
nonnegative. Our theorem implies a partial affirmative answer to a recent
conjecture of Yibo Gao about principal specializations of Schubert polynomials.
We propose a general framework for finding inclusion-exclusion inspired
expression of Schubert polynomials of all permutations.
