Codeforces Round 851 (Div. 2) |
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Finished |
You are given a sequence $$$a_1, a_2, \ldots, a_n$$$. Each element of $$$a$$$ is $$$1$$$ or $$$2$$$.
Find out if an integer $$$k$$$ exists so that the following conditions are met.
If there exist multiple $$$k$$$ that satisfy the given condition, print the smallest.
Each test contains multiple test cases. The first line contains the number of test cases $$$t$$$ ($$$1 \le t \le 100$$$). Description of the test cases follows.
The first line of each test case contains one integer $$$n$$$ ($$$2 \leq n \leq 1000$$$).
The second line of each test case contains $$$n$$$ integers $$$a_1, a_2, \ldots, a_n$$$ ($$$1 \leq a_i \leq 2$$$).
For each test case, if there is no such $$$k$$$, print $$$-1$$$.
Otherwise, print the smallest possible $$$k$$$.
362 2 1 2 1 231 2 141 1 1 1
2 -1 1
For the first test case, $$$k=2$$$ satisfies the condition since $$$a_1 \cdot a_2 = a_3 \cdot a_4 \cdot a_5 \cdot a_6 = 4$$$. $$$k=3$$$ also satisfies the given condition, but the smallest should be printed.
For the second test case, there is no $$$k$$$ that satisfies $$$a_1 \cdot a_2 \cdot \ldots \cdot a_k = a_{k+1} \cdot a_{k+2} \cdot \ldots \cdot a_n$$$
For the third test case, $$$k=1$$$, $$$2$$$, and $$$3$$$ satisfy the given condition, so the answer is $$$1$$$.
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