8112853 - [USACO06DEC]Cow Picnic S

The cows are having a picnic! Each of Farmer John's K (1 ≤ K ≤ 100) cows is grazing in one of N (1 ≤ N ≤ 1,000) pastures, conveniently numbered 1...N. The pastures are connected by M (1 ≤ M ≤ 10,000) one-way paths (no path connects a pasture to itself).

The cows want to gather in the same pasture for their picnic, but (because of the one-way paths) some cows may only be able to get to some pastures. Help the cows out by figuring out how many pastures are reachable by all cows, and hence are possible picnic locations.

K(1≤K≤100)只奶牛分散在N(1≤N≤1000)个牧场．现在她们要集中起来进餐．牧场之间有M(1≤M≤10000)条有向路连接，而且不存在起点和终点相同的有向路．她们进餐的地点必须是所有奶牛都可到达的地方．那么，有多少这样的牧场呢？

Line 1: Three space-separated integers, respectively: K, N, and M

Lines 2..K+1: Line i+1 contains a single integer (1..N) which is the number of the pasture in which cow i is grazing.

Lines K+2..M+K+1: Each line contains two space-separated integers, respectively A and B (both 1..N and A != B), representing a one-way path from pasture A to pasture B.

第1行：三个以空格分隔的整数，分别为：K，N和M

第2..K + 1行：第i + 1行包含一个整数（1..N），该整数是i放牧的牧场的编号。

行K + 2 . .M+K+1:每行包含两个用空格分隔的整数，分别是A和B(都是1..N和A != B)，表示从牧场A到牧场B的单向路径

Line 1: The single integer that is the number of pastures that are reachable by all cows via the one-way paths.

第1行:单个整数，它是所有奶牛通过单向路径可到达的牧场数量。

The cows can meet in pastures 3 or 4.

奶牛可以在牧场3或4集合。