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There are $8436$ steel balls, each with a radius of $1$ centimeter, stacked in a pile, with $1$ ball on top, $3$ balls in second layer, $6$ in the third layer, $10$ in the fourth, and so on. The number of horizontal layers in the pile is

1. $34$
2. $38$
3. $36$
4. $32$

1
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