let N = Int(readLine()!)!
let S = Array(readLine()!)
var v = 0
var c = 0
while c < (N - 2){
    if S[c] == "U"{
        for i in 1...(N-c-3)/2+1{
            if S[c+i] == "M"{
                if S[c+i*2] == "G"{
                    v += 1
                }
            }
        }
    }
    c += 1
}
print(v)