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


ans = 0
for stride in range(1, N//2+1):
    for k in range(0+stride, N-stride+1):
        i = k - stride
        j = k + stride

        if j >= N:
            continue
        
        if S[i] == "U" and \
           S[k] == "M" and \
           S[j] == "G":
               ans += 1
print(ans)