from sys import stdin, stdout
hossz=int(stdin.readline())
lanc=stdin.readline()
if 'A' not in lanc or 'G' not in lanc or 'T' not in lanc: print(0)
else:    
    a=[0]; g=[0]; t=(hossz+1)*[0]
    for i in range(hossz):
         if lanc[i]=='A': a.append(i+1)
         if lanc[i]=='G': g.append(i+1)
         if lanc[i]=='T': t[i+1]=1
#    print('a:',a)
#    print('g:',g)
#    print('t:',t)
    gT=(len(g))*[0]

    for i in range(1,len(g)):
        for  j in range(g[i]+1,len(t)):
            gT[i]+=t[j]
#   print(gT)
    K=1
    ossz=0
    for i in range(1,len(a)):
        while g[K]<a[i] and K<len(g)-1: K+=1
        if g[K]<a[i]:break
        ossz+=gT[K]
    print(ossz)
    
'''
14
ACAGTAATTGAGTT
12
CAGTAATTGATA
12
CAATAATTAATA
'''