Problem D.Too Simple Input file: standard input Output file: standard output Time limit: 1 second Memory limit: 64 mebibytes Rhason Cheung had a simple problem, and asked Teacher Mai for help. But Teacher Mai thought this problem was too simple, sometimes naive. So she ask you for help. Teacher Mai has m functions f1, f2, . . . , fm : {1, 2, . . . , n} → {1, 2, . . . , n} (that means for all x ∈ {1, 2, . . . , n}, f(x) ∈ {1, 2, . . . , n}). But Rhason only knows some of these functions, and others are unknown. She wants to know how many different function series f1, f2, . . . , fm there are that for every i (1 ≤ i ≤ n), f1(f2(. . . fm(i))) = i. Two function series f1, f2, . . . , fm and g1, g2, . . . , gm are considered different if and only if there exist i (1 ≤ i ≤ m),j(1 ≤ j ≤ n),fi(j) 6= gi(j). Input First line of the input contains one integer T (1 ≤ T ≤ 50). For each test case, the first lines contains two numbers n and m (1 ≤ n, m ≤ 100). Then m lines follow. In i-th line, there is one number −1 or n space-separated integers. If there is only one number −1, the function fi is unknown. Otherwise the j-th number in the i-th line means fi(j). Output For each test case print the answer modulo 109 + 7. Example standard input standard output 1 3 3 1 2 3 -1 3 2 1 1
题目分析：check一下合法的方案，对于连续的-1，设其长度为k，则k-1个是n！种排列，其余一种是唯一方案。