# UUID: 79213380-e7df-4d70-a761-c0fef189fb49
"""
n = int(input())
s = input()
s.replace("C", "") #(ez nem szükséges)
a = 0
ag = 0
agt = 0

for i in s:
    if i == "A":
        a += 1
    elif i == "G" and a > 0:
        ag = a
    elif i == "T" and ag > 0:
        agt += ag
    #print(a, ag, agt)
print(agt)
"""
DNS_hossza = int(input())
DNS_lanc = list(input())
T_talalo = 0
DNS_hossza = len(DNS_lanc)

for i in range(DNS_hossza):
    if DNS_lanc[i] == "A":
        VoltG = False
        for j in range(i, DNS_hossza):
            if DNS_lanc[j] == "G":
                VoltG = True
            if DNS_lanc[j] == "T" and VoltG:
                T_talalo += 1

print(T_talalo)