#include <bits/stdc++.h>
using namespace std;

#define lp(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define rep(i, n) lp(i, 0, n)
#define rlp(i, a, b) for (int i = (int)(b) - 1; i >= (int)(a); i--)
#define rrep(i, n) rlp(i, 0, n)

#define mp make_pair
#define mt make_tuple
#define pb push_back
#define eb emplace_back
#define all(c) begin(c), end(c)

typedef long long ll;
typedef unsigned long long ull;

template<typename T>
inline void unique(T &c){
	sort(all(c));
	c.erase(unique(all(c)), end(c));
}

int n;
string s;

int main()
{
	cin >> n >> s;
	rep(i, n - 1){
		if (s[i] == s[i + 1]){
			cout << "YES\n";
			return 0;
		}
	}
	rep(i, n - 3){
		bool t = string(s, i, 4) == "1010"
		       | string(s, i, 4) == "0101";
		if (t){
			cout << "YES\n";
			return 0;
		}
	}
	cout << "NO\n";
}