# import sys; input = sys.stdin.buffer.readline
# sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	N = int(input())
	S = input()
	if N == 1:
		print("NO")
		return

	if N == 2:
		if S[0] != S[1]:
			print("NO")
		else:
			print("YES")
		return

	if N == 3:
		if S[0] == S[1] or S[1] == S[2]:
			print("YES")
		else:
			print("NO")
		return

	print("YES")

if __name__ == '__main__':
	main()