class UnionFind(val size: Int) {
    private val vec = IntArray(size){-1}
    fun find(a: Int): Int {
        return if (vec[a] < 0) {
            a
        }else {
            vec[a] = find(vec[a])
            vec[a]
        }
    }
    fun same(a: Int, b: Int): Boolean {
        return find(a) == find(b)
    }
    fun unite(a: Int, b: Int): Boolean {
        val ar = find(a)
        val br = find(b)
        if (ar == br) return false
        if (vec[ar] < vec[br]) {
            vec[ar] += vec[br]
            vec[br] = ar
        }else {
            vec[br] += vec[ar]
            vec[ar] = br
        }
        return true
    }
    fun sizeOf(a: Int): Int {
        return -vec[find(a)]
    }
}
fun main() {
    val (n, m) = readLine()!!.split(' ').map(String::toInt)
    val a = readLine()!!.split(' ').map(String::toInt)
    val b = readLine()!!.split(' ').map(String::toInt)
    val uft = UnionFind(n + m + 1)
    val allCell = (a + b).sorted()
    for (i in 0 until n + m) {
        if (a.binarySearch(allCell[i]) >= 0) {
            uft.unite(i, n + m)
        }
    }
    var result = 0
    for (i in (1 until n + m).sortedBy { allCell[it] - allCell[it - 1] }) {
        if (uft.unite(i, i - 1)) {
            result += allCell[i] - allCell[i - 1]
        }
    }
    println(result)
}