fun main() {
    readln().toInt()
    val s = readln()

    val counts = Array(26) { 0 }

    var f = true
    for(c in s) {
        when {
            counts[c - 'A'] == 0 -> counts[c - 'A']++
            else -> {
                f = false
                break
            }
        }
    }

    if(f) println("Yes")
    else println("No")
}