N = int(input())

S = input()

ans = 0

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