import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		char[] s = sc.next().toCharArray();
		sc.close();

		long ans = 0;
		long[][][][] dp = new long[5][26][26][26];
		for (int i = 0; i < n; i++) {
			int c = s[i] - 'A';

			for (int j = 0; j < 26; j++) {
				if (j == c) {
					continue;
				}
				for (int j2 = 0; j2 < 26; j2++) {
					if (j2 == c || j2 == j) {
						continue;
					}
					for (int j3 = 0; j3 < 26; j3++) {
						if (j3 == c || j3 == j || j3 == j2) {
							continue;
						}
						ans += dp[4][j][j2][j3];
					}
				}
			}
			for (int j = 0; j < 26; j++) {
				for (int j2 = 0; j2 < 26; j2++) {
					if (j != j2 && j != c && j2 != c) {
						dp[4][j][j2][c] += dp[3][j][j2][0];
					}
				}
			}
			for (int j2 = 0; j2 < 26; j2++) {
				if (j2 != c) {
					dp[3][c][j2][0] += dp[2][c][j2][0];
				}
			}
			for (int j = 0; j < 26; j++) {
				if (j != c) {
					dp[2][j][c][0] += dp[1][j][0][0];
				}
			}
			dp[1][c][0][0]++;
		}
		System.out.println(ans);
	}
}