module main;
// https://yukicoder.me/problems/no/290/editorial より
import std;

void main()
{
	// 入力
	int N = readln.chomp.to!int;
	auto S = readln.chomp;
	// 答えの計算と出力
	if (N == 1)
		writeln("NO");
	else if (N == 2) {
		if (S[0] == S[1])
			writeln("YES");
		else
			writeln("NO");
	} else if (N == 3) {
		if (S[0] == S[1] || S[1] == S[2])
			writeln("YES");
		else
			writeln("NO");
	} else
		writeln("YES");
}