A sample (349 mg) of an oligomeric protein of Mr 167,000 was treated with an excess of 1‑fluoro‑2,4‑dinitrobenzene (Sanger's reagent) under slightly alkaline conditions until the chemical reaction was complete. The peptide bonds of the protein were then completely hydrolyzed by heating it with concentrated HCl. The hydrolysate was found to contain 3.55 mg of DNP‑Val. 2,4‑Dinitrophenyl derivatives of the α‑amino groups of other amino acids could not be found. Calculate the number of polypeptide chains in this protein. Give the answer as a whole number.