import sys
import os


IS_LOCAL = os.environ.get("LOCAL") == "true"


def debug(*args, sep=" ", end="\n", flush=False) -> None:
    if IS_LOCAL:
        print(*args, sep=sep, end=end, file=sys.stderr, flush=flush)


def yn(flg: bool) -> bool:
    print('Yes' if flg else 'No')
    return flg


def gcd(a, b):
    a = abs(a); b = abs(b)
    if a < b: a, b = b, a
    while b > 0:
        a, b = b, a % b
    return a


def lcm(a, b):
    return a * b // gcd(a, b)


def main():
    readline = sys.stdin.readline

    N = int(readline())
    A = list(map(int, readline().split()))
    yn(any(A[i] == A[i + 1] for i in range(N - 1)) or any(A[i] == A[i + 2] for i in range(N - 2)))


if __name__ == "__main__":
    main()