import bisect
N=int(input())
S=list(input())

A=[]
B=[]
C=[]
for i in range(N):
    if S[i]=="U":
        A.append(i)
    elif S[i]=="M":
        B.append(i)
    else:
        C.append(i)
        
cnt=0
for b in range(len(B)):
    for a in range(len(A)):
        if A[a]>B[b]:
            break
        else:
            if C==[]:
                break
            elif C[len(C)-1]>=B[b]+(B[b]-A[a]):
                #print(bisect.bisect_left(C,B[b]+(B[b]-A[a])))
                if C[bisect.bisect_left(C,B[b]+(B[b]-A[a]))]==B[b]+(B[b]-A[a]):
                    cnt+=1
print(cnt)