#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const ll INF = 1ll<<60;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

int main() {
	int n;
	string s;
	cin >> n >> s;
	
	bool ans = false;
	REP(i, s.size() - 1) if (s[i] == s[i + 1]) ans = true;
	if (s.size() >= 4) ans = true;
	
	puts(ans ? "YES" : "NO");
	return 0;
}