# coding: utf-8
# Your code here!
N=int(input())
S=list(input())
ans=0
for i in range(N):#スタートの添え字
    for d in range((N-i)-1//2):
        if S[i]=="U":
            if S[i+d]=="M" and S[i+2*d]=="G":
                ans+=1
print(ans)