Let $p_1 = 2$, $p_2 = 3$, $p_3 = 5$, ... be the sequence of prime numbers. Find the least positive even integer $n$ such that $p_1 + p_2 + p_3 + \ldots + p_n$ is not a prime number.

Let's think step by step and output the final answer within \boxed{}.
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