CF1788A One and Two

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. - $ 1 \leq k \leq n-1 $ , and - $ a_1 \cdot a_2 \cdot \ldots \cdot a_k = a_{k+1} \cdot a_{k+2} \cdot \ldots \cdot a_n $ . 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 $ .

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 $ .