fun main(args: Array<String>) {
    val n = readLine()!!.toInt()
    val s = readLine()!!
    
    var c = 0
    for (i in 0..(n - 3)) {
        if (!s[i].equals('U')) continue
        for (d in 1..((n - 1 - i) / 2)) {
            val j = i + d
            val k = j + d
            if (s[j].equals('M') && s[k].equals('G')) c++
        }
    }
    println(c)
}