Score : 300 points
There are N observatories in AtCoder Hill, called Obs. 1, Obs. 2, ..., Obs. N. The elevation of Obs. i is H_i. There are also M roads, each connecting two different observatories. Road j connects Obs. A_j and Obs. B_j.
Obs. i is said to be good when its elevation is higher than those of all observatories that can be reached from Obs. i using just one road. Note that Obs. i is also good when no observatory can be reached from Obs. i using just one road.
How many good observatories are there?
Input is given from Standard Input in the following format:
N M H_1 H_2 ... H_N A_1 B_1 A_2 B_2 : A_M B_M
Print the number of good observatories.
4 3 1 2 3 4 1 3 2 3 2 4
2
From Obs. 1, you can reach Obs. 3 using just one road. The elevation of Obs. 1 is not higher than that of Obs. 3, so Obs. 1 is not good.
From Obs. 2, you can reach Obs. 3 and 4 using just one road. The elevation of Obs. 2 is not higher than that of Obs. 3, so Obs. 2 is not good.
From Obs. 3, you can reach Obs. 1 and 2 using just one road. The elevation of Obs. 3 is higher than those of Obs. 1 and 2, so Obs. 3 is good.
From Obs. 4, you can reach Obs. 2 using just one road. The elevation of Obs. 4 is higher than that of Obs. 2, so Obs. 4 is good.
Thus, the good observatories are Obs. 3 and 4, so there are two good observatories.
6 5 8 6 9 1 2 1 1 3 4 2 4 3 4 6 4 6
3