import collections
N = int(input())
S= input()
U = []
M = []
G = collections.defaultdict(int)
for i in range(N):
    if S[i]=='U':
        U.append(i)
    elif S[i]=='M':
        M.append(i)
    else:
        G[i]=1

ans = 0
for u in U:
    for m in M:
        if u<m and G[u+(m-u)*2]==1:
            ans+=1
print(ans)