O=C1C[C@@H](C(=O)OCc2ccccc2)NC(=O)C[C@@H](C(=O)OCc2ccccc2)NC(=O)C[C@@H](C(=O)OCc2ccccc2)N1
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.