import sys


def input(): return sys.stdin.readline().rstrip('\n')


def main():
    N = int(input())
    *A, = map(int, input().split())
    for i in range(N-1):
        if A[i] == A[i+1]:
            print('Yes')
            return
    for i in range(N-2):
        if A[i] == A[i+2]:
            print('Yes')
            return
    print('No')


if __name__ == '__main__':
    main()