N = int(input())
S = input()
cnt=0
for i in range(len(S)-2):
    if S[i]=='U':
        for j in range(i+1, len(S)-1):
            if S[j]=='M':
                if j+j-i<len(S):
                    if S[j+j-i]=='G':cnt=cnt+1
print(cnt)