#include <bits/stdc++.h>

using namespace std;
#define fast_io ios_base::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL)
#define pb push_back
#define int long long
#define ll long long
#define ld long double

#define rep(i, n) for (ll i=0; i<n; i++)
#define repi1(i, n) for (ll i = n; i >=0; i--)
#define mem(v, ha) memset(v, ha, sizeof(v))
#define all(a)  a.begin(), a.end()
#define allr(a)  a.rbegin(), a.rend()
#define CLOCK cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
typedef vector<ll> vi;
typedef vector<vector<int>> vvi;
typedef vector<pair<ll, ll>> vpi;
typedef vector<char> vc;
#define no cout << "NO\n"
#define yes cout << "YES\n"
#define mp make_pair
#define ff first
#define ss second
const ll M = 1e9 + 7;
const ll mod = 998244353 ;

const long double PI = 3.141592653589793238460;
const int inf = (int)(1e9);

// auto sum=[&](int use, int y){return use+y;};

void solve()
{

    int N;
    cin >> N;
    string S;
    cin >> S;
/*    if (n == 1)
    {
        no;
        return;
    }
    if (n == 2)
    {
        if (s[0] == s[1])
            yes;
        else
            no;
        return;
    }
    if (n == 3)
    {
        if (s[0] == s[1] || s[1] == s[2])
            yes;
        else
            no;
        return;
    }
    if (n >= 4)
        yes;*/

    if (N >= 4) {
    cout << "YES" << endl;
  } else if (N == 1) {
    cout << "NO" << endl;
  } else {
    // N==2, 3
    bool ok = false;
    for (ll i = 0; i + 1 < N; i++) {
      if (S[i] == S[i + 1]) {
        ok = true;
        break;
      }
    }
    if (ok) {
      cout << "YES" << endl;
    } else {
      cout << "NO" << endl;
    }
  }



}

int32_t main()
{
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif


    fast_io;
    int T = 1;
    // cin >> T;


    while (T--)
    {
        solve();


    }

}