package chelper;

import io.InputReader;
import io.OutputWriter;

public class Hanoi {
  public void solve(int testNumber, InputReader in, OutputWriter out) {
    int n = in.nextInt();
    int[] a = new int[n];

    String s = in.nextString();
    for (int i = 0; i < n; i++) {
      a[i] = s.charAt(i) - 'A';
    }

    for (int i = n - 1; i >= 0; i--) {
      if (a[i] == 2) {
        out.println("NO");
        return;
      }

      if (a[i] == 1) {
        for (int j = 0; j < n; j++) {
          if (a[j] < 2) {
            a[j] = (1 + a[j]) % 2;
          }
        }
      }

      for (int j = 0; j < n; j++) {
        if (a[j] > 1) {
          a[j] = 1 + a[j] % 2;
        }
      }
    }

    out.println("YES");
  }
}