n = int(input())
a = list(map(int, input().split()))

for i in range(n - 1):
    a[i], a[i + 1] = a[i + 1], a[i]
    for j in range(n - 1):
        if a[j] == a[j + 1]:
            print("Yes")
            exit()
    a[i], a[i + 1] = a[i + 1], a[i]

print("No")