O=C1c2cccnc2C(=O)c2c1nc1ccccc1c2-c1cncc(-c2c3c(nc4ccccc24)C(=O)c2cccnc2C3=O)c1
PSA is a commonly used medicinal chemistry metric for the optimization of a drug's ability to permeate cells. Please predict psa of this molecule.