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

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

print(ans)