#include<stdio.h>
int main()
{
	int n;
	scanf("%d", &n);
	char s[32];
	scanf("%s", s);
	int i, j, k, l, m;
	int ans = 0;
	for (i = 0; i < n; i++)
		for (j = i + 1; j < n; j++)
			for (k = j + 1; k < n; k++)
				for (l = k + 1; l < n; l++)
					for (m = l + 1; m < n; m++)
						if (s[i] != s[j] && s[i] == s[k] && s[i] != s[l] && s[i] != s[m] && s[j] != s[l] && s[j] != s[m] && s[l] != s[m])
							ans++;
	printf("%d\n", ans);
	return 0;
}