n = int(input())
a = list(map(int, input().split()))
for i in range(n-1):
    if a[i] == a[i+1]:
        print("Yes")
        exit()
default = a.copy()
for i in range(n-1):
    a[i],a[i+1] = a[i+1],a[i]
    for i in range(n-1):
        if a[i] == a[i+1]:
            print("Yes")
            exit()
    a = default
print("No")