N = int(input())
S = input()
ans = 0
for i in range(N):
    if S[i] != "U":
        continue
    for j in range(i+1, N):
        if S[j] != "M":
            continue
        d = j-i
        if j+d >= N:
            break
        if S[j+d] == "G":
            ans += 1

print(ans)