import sys

int1 = lambda x: int(x) - 1

# input = lambda: sys.stdin.buffer.readline()
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
i1 = lambda: int1(input())
mi = lambda: map(int, input().split())
mi1 = lambda: map(int1, input().split())
li = lambda: list(mi())
li1 = lambda: list(mi1())
lli = lambda n: [li() for _ in range(n)]

INF = float("inf")
mod = int(1e9 + 7)
# mod = 998244353

n, m = mi()
s, t = mi1()
g = [list() for i in range(n)]
for i in range(m):
    a, b = mi1()
    g[a].append(b)
    g[b].append(a)
exit(0)
ng = [False] * n
input()
for i in li1():
    ng[i] = True

from collections import deque

que = deque()
que.append(s)
dp = [INF] * n
dp[s] = 0
while que:
    cur = que.popleft()
    for to in g[cur]:
        if ng[to]:
            continue
        if dp[to] > dp[cur] + 1:
            dp[to] = dp[cur] + 1
            que.append(to)
print("Yes" if not ng[s] and dp[t] != INF else "No")