N = int(input())
S = input()
count = 0
for i in range(N - 2):
    if S[i] != "U":
        continue
    for k in range(i + 2,N):
        if S[k] != "G":
            continue
        if not (i + k) % 2:
            if S[(i + k) // 2] == "M":
                count+=1
print(count)