N = int(input())
S = input()
count = 0
for i in range(N - 2):
    if S[i] != "U":
        continue
    for j in range(i + 1,N - 1):
        if S[j] != "M":
            continue
        for k in range(j + 1,N):
            if j - i != k - j:
                continue
            if S[k] == "G":
                count+=1
print(count)