B"Valera conducts experiments with algorithms that search for shortest paths. He has recently studied the Floyd's algorithm, so it's time to work with it. Valera's already written the code that counts the shortest distance between any pair of vertexes in a non-directed connected graph from n vertexes and m edges, containing no loops and multiple edges. Besides, Valera's decided to mark part of the vertexes. He's marked exactly k vertexes a1, xe2 x80 x89a2, xe2 x80 x89..., xe2 x80 x89ak. Valera's code is given below. Valera has seen that his code is wrong. Help the boy. Given the set of marked vertexes a1, xe2 x80 x89a2, xe2 x80 x89..., xe2 x80 x89ak, find such non-directed connected graph, consisting of n vertexes and m edges, for which Valera's code counts the wrong shortest distance for at least one pair of vertexes (i, xe2 x80 x89j). Valera is really keen to get a graph without any loops and multiple edges. If no such graph exists, print -1. The first line of the input contains three integers n, xe2 x80 x89m, xe2 x80 x89k (3 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89300, 2 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89k xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n , ) -- the number of vertexes, the number of edges and the number of marked vertexes. The second line of the input contains k space-separated integers a1, xe2 x80 x89a2, xe2 x80 x89... ak (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89ai xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n) -- the numbers of the marked vertexes. It is guaranteed that all numbers ai are distinct. If the graph doesn't exist, print -1 on a single line. Otherwise, print m lines, each containing two integers u, xe2 x80 x89v -- the description of the edges of the graph Valera's been looking for."...