from itertools import combinations

n = int(input())
s = input()

if n <= 4:
    print(0)

def count_valid_combinations(s):
    count = 0
    for combo in combinations(s, 5):
        if combo[0] != combo[2]:
            continue
        if len(set(combo)) == 4:
            count += 1
    return count
    
if n>= 5:
    print(count_valid_combinations(s))