A biochemistry student was instructed to use cation-exchange chromatography to separate a mixture of four amino acids (Gly (pkg = 2.34, 9.60), Arg (pka = 2.17, 9.04, 12.48), Gin (pkg = 2.17, 9.13), Lys (pkg = 2.18, 8.95, 10.53)]. She decided to pack the column with "Dowex-50" (a resin/polymer typically used in cation-exchange columns). List the amino acids in decreasing order of interaction with the column at pH 7 (i.e., most strongly bound amino acid listed first)