def solve() : 
    N = int(input())
    S = input()
    ans = 0
    for i in range(N) :
        if S[i]!='U' : continue
        K = (N-i-1)//2
        for j in range(K+1) : 
            if S[i+j]=='M' and S[i+2*j]=='G' : ans+=1
    print(ans)
solve()