N = int(input())
S = input()
v = 0
c = 0
while c < N-1:
    c = S.find("U",c)
    if c < 0:break
    for i in range(0,(N-c-3)//2+1):
        if S[c+i+1] != "M":
            continue
        elif S[c+i*2+2] == "G":
            v += 1
    c += 1
print(v)