#include "bits/stdc++.h" #include #define _CRT_SECURE_NO_WARNINGS #define ALL(a) (a).begin(),(a).end() #define SORT(c) sort((c).begin(),(c).end()) #define DESCSORT(c) sort(c.begin(), c.end(), greater()) using namespace std; const int dy[] = { 0, 1, 0, -1 }; const int dx[] = { 1, 0, -1, 0 }; using LL = long long int; using LD = long double; const int INF = (1 << 30) - 1; const LL INF64 = ((LL)1 << 62) - 1; const double PI = 3.1415926535897932384626433832795; using pii = pair; using pll = pair; using pdd = pair; using vi = vector; using vvi = vector; using vvvi = vector; using vl = vector; using vvl = vector; using vvvl = vector; using vd = vector; using vvd = vector; using vs = vector; using vb = vector; using vvb = vector; int n; string s; bool solve() { if (4 <= n) { return true; } if (n == 1) { return false; } else if (n == 2) { if (s[0] == s[1]) return true; else return false; } else { if (s[0] == s[1] || s[1] == s[2] || s[0] == s[2]) return true; else return false; } return false; } int main() { ios::sync_with_stdio(false); cin.tie(0); cin >> n >> s; cout << (solve() ? "YES" : "NO") << endl; return 0; }