N = int(input())
S = list(input())

c = S.count("U")
count = 0
i = 0
while c > 0:
    if S[i] == "U":
        for j in range(int((N-i-1)/2)):
            if S[i+j+1] == "M" and S[i+2*(j+1)]  == "G":
                count += 1
        c -= 1
    i += 1
    
print(count)