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