fun main() {
    val (n, c) = readInts()
    val dp = Array(n + 1) { IntArray(n + 1) { Int.MAX_VALUE } }
    for (i in 1 .. n) {
        dp[i][i] = i
    }
    for (len in 2 .. n) {
        for (i in 1 .. n - len + 1) {
            val j = i + len - 1
            for (k in i..j) {
                var r = k
                if (i != k) r = maxOf(r, dp[i][k-1] + k)
                if (j != k) r = maxOf(r, dp[k + 1][j] + c)
                dp[i][j] = minOf(dp[i][j], r)
            }
        }
    }
    println(dp[1][n])
}

private fun readInt() = readln().toInt()
private fun readLongs() = readStrings().map { it.toLong() }
private fun readStrings() = readln().split(" ")
private fun readInts() = readStrings().map { it.toInt() }