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

ans = 0
for i in range(N) :
    if S[i] == "M" :
        a = min(i, N-1-i)
        for j in range(1,a+1) :
            if (S[i-j] == "U") and (S[i+j] == "G") :
                ans += 1
print(ans)