#include <iostream>
#include <algorithm>
#include <utility>

using namespace std;


int binarySearch(int arr[], int l, int r, int x)
{
    int mid = l + (r - l) / 2;
    if (r >= l)
    {

        // If the element is present at the middle
        // itself
        if (arr[mid] <= x)
            return mid;

        // If element is smaller than mid, then
        // it can only be present in left subarray
        if (arr[mid] > x)
            return binarySearch(arr, l, mid - 1, x);

        // Else the element can only be present
        // in right subarray
        return binarySearch(arr, mid + 1, r, x);
    }

    // We reach here when element is not
    // present in array
    return mid;
}

int main()
{
    int r = 0;
    int n, m;
    cin >> n >> m;
    int *a = new int[n + m];
    int *k = new int[m];
    int p = 0;
    for (int i = 0; i < n; i++)
    {
        cin >> a[i];
    }

    for (int i = 0; i < m; i++)
    {
        cin >> k[i];
    }

    int index;

    while (p < m)
    {
        if (k[p] >= a[n + p - 1])
        {
            a[n + p] = k[p];
            p++;
        }
        else
        {
            index = binarySearch(a, 0, n + m, k[p]);
            while (a[index] <= k[p])
            {
                index++;
            }
            r++;
            swap(k[p], a[index]);
        }
    }
    cout << r << endl;
    return 0;
}