The teacher asked Xiaoming to write 3 non-zero natural numbers, and the sum of the 3 numbers is 9. If the numbers are the same and the order is not the same way of writing, for example, 1+2+6, 2+1+6 and 6+1+ 2 are all written in the same way. May I ask: How many different ways of writing Xiao Ming?
老师让小明写出3个非零的自然数，且3个数的和是9，如果数相同、顺序不算同一种写法，例如1+2+6、2+1+6还有6+1+2都算是同一种写法．请问：小明共有多少种不同的写法？
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