{"trustable":false,"prependHtml":"\u003cscript\u003e window.katexOptions \u003d { disable: true }; \u003c/script\u003e\n\u003cscript type\u003d\"text/x-mathjax-config\"\u003e\n MathJax.Hub.Config({\n tex2jax: {\n inlineMath: [[\u0027$$$\u0027,\u0027$$$\u0027], [\u0027$\u0027,\u0027$\u0027]],\n displayMath: [[\u0027$$$$$$\u0027,\u0027$$$$$$\u0027], [\u0027$$\u0027,\u0027$$\u0027]]\n }\n });\n\u003c/script\u003e\n\u003cscript async src\u003d\"https://mathjax.codeforces.org/MathJax.js?config\u003dTeX-AMS-MML_HTMLorMML\" type\u003d\"text/javascript\"\u003e\u003c/script\u003e","sections":[{"title":"","value":{"format":"HTML","content":"\u003cscript type\u003d\u0027text/x-mathjax-config\u0027\u003eMathJax.Hub.Config({tex2jax: { inlineMath: [[\u0027$\u0027,\u0027$\u0027]] } }); \u003c/script\u003e\n\u003cscript type\u003d\u0027text/javascript\u0027 src\u003d\u0027https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config\u003dTeX-AMS-MML_HTMLorMML\u0027\u003e\u003c/script\u003e\n\u003cscript type\u003d\u0027text/javascript\u0027\u003esetTimeout(function(){MathJax.Hub.Queue([\u0027Typeset\u0027, MathJax.Hub, \u0027left_view\u0027]);}, 2000);\u003c/script\u003e\n\u003cdiv class\u003d\"panel_content\"\u003e\n Alice is planning her travel route in a beautiful valley. In this valley, there are $N$ lakes, and $M$ rivers linking these lakes. Alice wants to start her trip from one lake, and enjoys the landscape by boat. That means she need to set up a path which go through every river exactly once. In addition, Alice has a specific number ($a_1, a_2, ... , a_n$) for each lake. If the path she finds is $P_0 \\rightarrow P_1 \\rightarrow ... \\rightarrow P_t$, the lucky number of this trip would be $a_{P_0} \\quad XOR \\quad a_{P_1} \\quad XOR \\quad... \\quad XOR \\quad a_{P_t}$. She want to make this number as large as possible. Can you help her? \n\u003c/div\u003e"}},{"title":"Input","value":{"format":"HTML","content":"The first line of input contains an integer $t$, the number of test cases. $t$ test cases follow. \n\u003cbr\u003e \n\u003cbr\u003eFor each test case, in the first line there are two positive integers $N~(N \\leq 100000)$ and $M~(M \\leq 500000)$, as described above. The $i$-th line of the next $N$ lines contains an integer $a_i(\\forall i, 0 \\leq a_i \\leq 10000)$ representing the number of the $i$-th lake. \n\u003cbr\u003e \n\u003cbr\u003eThe $i$-th line of the next $M$ lines contains two integers $u_i$ and $v_i$ representing the $i$-th river between the $u_i$-th lake and $v_i$-th lake. It is possible that $u_i\u003dv_i$."}},{"title":"Output","value":{"format":"HTML","content":"For each test cases, output the largest lucky number. If it dose not have any path, output \"Impossible\"."}},{"title":"Sample Input","value":{"format":"HTML","content":"\u003cpre\u003e2\n3 2\n3\n4\n5\n1 2\n2 3\n4 3\n1\n2\n3\n4\n1 2\n2 3\n2 4\u003c/pre\u003e"}},{"title":"Sample Output","value":{"format":"HTML","content":"\u003cpre\u003e2\nImpossible\u003c/pre\u003e"}}]}