Problem

Problem

Let f:[0,∞)→[0,∞)f: [0, \infty) \rightarrow [0, \infty) be a function defined by f(x)=x2+(k2−3k+2)x+k2−kf(x) = x^2 + (k^2 - 3k + 2)x + k^2 - k. If f(x)f(x) is both injective and surjective, then the number of integers in the range of kk is

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