O=C(CCCCCCCCC(=O)OCC1OC(n2cnc3c(=O)[nH]cnc32)C(O)C1O)OCC1OC(n2cnc3c(=O)[nH]cnc32)C(O)C1O
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.