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