#include<iostream>
#include<string>

using namespace std;
int main(){
  string s;
  int n;
  cin >> n;
  if(n>3){
    cout<<"YES"<<endl;
    return 0;
  }else{
    cin >>s ;
    if(n==1){
      cout<<"NO"<<endl;
      return 0;
    }
    if(n==2){
      if(s[0]==s[1]){
        cout<<"YES"<<endl;
      }else{
        cout<<"NO"<<endl;
      }
    }
    if(n==3){
      if(s[0]==s[1] || s[1]==s[2]){
        cout<<"YES"<<endl;
      }else{
        cout<<"NO"<<endl;
      }
    }
  }
  return 0;
}