B'In order to win his toughest battle, Mircea came up with a great strategy for his army. He has n soldiers and decided to arrange them in a certain way in camps. Each soldier has to belong to exactly one camp, and there is one camp at each integer point on the x -axis (at points cdots, -2, -1, 0, 1, 2, cdots ). The strategy consists of m conditions. Condition i tells that soldier a_i should belong to a camp that is situated d_i meters in front of the camp that person b_i belongs to. (If d_i < 0 , then a_i 's camp should be -d_i meters behind b_i 's camp.) Now, Mircea wonders if there exists a partition of soldiers that respects the condition and he asks for your help! Answer "YES" if there is a partition of the n soldiers that satisfies all of the m conditions and "NO" otherwise. Note that two different soldiers may be placed in the same camp. The first line contains a single integer t ( 1 <= q t <= q 100 ) -- the number of test cases. The first line of each test case contains two positive integers n and m ( 2 <= q n <= q 2 cdot 10^5 ; 1 <= q m <= q n ) -- the number of soldiers, and the number of conditions respectively. Then m lines follow, each of them containing 3 integers: a_i , b_i , d_i ( a_i neq b_i ; 1 <= q a_i, b_i <= q n ; -10^9 <= q d_i <= q 10^9 ) -- denoting the conditions explained in the statement. Note that if d_i is positive, a_i should be d_i meters in front of b_i and if it is negative, a_i should be -d_i meters behind b_i . Note that the sum of n over all test cases doesn 't exceed 2 cdot 10^5 . For each test case, output "YES" if there is an arrangement of the n soldiers that satisfies all of the m conditions and "NO" otherwise. For the first test case, we can partition the soldiers into camps in the following way'...