ans=0
n=int(input())
s=list(input())
for i in range(n):
    for j in range(i+1,n):
        k=2*j-i
        if n-1<k or k<0:
            continue 
        if i<j<k and s[i]=="U" and s[j]=="M" and s[k]=="G":
            ans+=1
print(ans)