# UUID: ab583c88-80e7-467c-816a-73072c2d0746
"""n = int(input())
s = input()
s = 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)
"""
import sys
input = sys.stdin.readline

def solve():
    DNS_hossza = int(input())
    DNS_lanc = 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)
solve()