kilkist = int(input())
kolo = input().split()
x = 0
canornot = "No"
perviposl = [kolo[0], kolo[-1]]

for i in range(kilkist):
    if i == kilkist:
        i = 0
    iplusodin = i + 1
    iplusdwa = i + 2
    if iplusdwa >= kilkist - 1:
        iplusdwa = iplusdwa - (kilkist - 1)
    if iplusodin >= kilkist - 1:
        iplusodin = iplusodin - (kilkist - 1)
    if kolo[i] == kolo[iplusodin] and kolo[i] == kolo[iplusdwa]:
        canornot = "Yes"
        print(canornot)
        exit()

    if kolo[i] == kolo[iplusodin]:
        x = kolo[i]
        for j in range(i + 1, kilkist):
            if j == kilkist:
                j = 0
            jplusodin = j + 1
            if jplusodin >= kilkist - 1:
                jplusodin = jplusodin - kilkist
            if kolo[j] == x and kolo[jplusodin] == x:
                canornot = "Yes"
                print(canornot)
                exit()

print(canornot)