n = list(map(int, input().split()))[0]
a = list(map(int, input().split()))

def yn(ans):
    if ans:
        print("Yes")
    else:
        print("No")


def solve():
    if n == 2:
        yn(a[0] == a[1])
        return
    if n == 3:
        yn(a[0] == a[2])
        return
    ans1 = any([a[i] == a[i + 1] for i in range(len(a) - 1)])
    ans2 = any([a[i] == a[i + 2] for i in range(len(a) - 2)])
    yn(ans1 or ans2)

if __name__ == '__main__':
    solve()