#include "bits/stdc++.h"
using namespace std;

int n;
char s[1000010];

int main() {
    scanf("%d", &n);
    scanf("%s", s);
    if (n < 3) {
        puts(n == 1 ? "NO" : s[0] == s[1] ? "YES" : "NO");
        return 0;
    }

    if (n == 3) {
        puts(s[0]==s[1] || s[1]==s[2] ? "YES" : "NO");
        return 0;
    }

    puts("YES");
    return 0;
}