N = int(input())
S = input()

ans = 0
for i in range(N):
    for j in range(N):
        if i+j>=N: break
        if S[i]!='U' : continue
        if j==0 or (i+j)%2==1:
            continue
        if S[(i+j)//2]=='M' and S[i+j]=='G':
            ans += 1
print(ans)