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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