# GCD = 1

For a positive integer $$n>2,$$ what can we say about the number of positive integers less than $$n$$ that are relatively prime to $$n$$ (that is, their GCD is 1)?

Hint: A useful property of the Greatest Common Divisor function is $$\gcd(a,b) = \gcd(a,a-b);$$ e.g., $$\gcd(10,8) = \gcd(10,2) = 2.$$

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