N=int(input())
S=list(input())
cnt=0
for i in range(N):
    for k in range(i+1,N):
        if (k*2-i)>=N or k*2-i<0: continue
        if S[i]=="U" and S[k]=="M" and S[k*2-i]=="G":
            cnt+=1
print(cnt)