from itertools import combinations
n=int(input())
s=list(input())
idx=[i for i in range(n)]
idx=list(combinations(idx,5))
ans=0
for ord in idx:
    word=[]
    for i in ord:
        word.append(s[i])
    if word[0]==word[2] and word[1]!=word[3] and word[3]!=word[4] and word[1]!=word[4] and len(set(word))==4 and word[0]!=word[1] and word[0]!=word[3] and word[0]!=word[4]:
        ans+=1
print(ans)