dfs.py

#!/usr/bin/python3
# file: dfs.py

n, m = map(int, input().split())
graph = [[] for i in range(n)]
for i in range(m):
    a, b = map(int, input().split())
    graph[a].append(b)

vis = [False for i in range(n)]


def dfs(v, dest):
    vis[v] = True
    f = False
    if v == dest:
        f = True
    for u in graph[v]:
        if not vis[u]:
            f |= dfs(u, dest)
    return f


u, v = map(int, input().split())
if dfs(u, v):
    print("YES")
else:
    print("NO")