#include <bits/stdc++.h>
#define PB push_back
#define MP make_pair
#define REP(i,n) for (int i=0;i<(n);i++)
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define ALL(a) (a).begin(),(a).end()
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
const int INF=1e9;
int main(){
      int n;
      string s;
      cin>>n>>s;
      REP(i,n-1){
            if(s[i]==s[i+1]){
                  cout<<"YES"<<endl;
                  return 0;
            }
      }
      if(n>=4)cout<<"YES"<<endl;
      else cout<<"NO"<<endl;
      return 0;
}