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

using namespace std;

void print(int a[], int n)
{
    for (int i = 0; i < n; i++)
    {
        cout << a[i] << " ";
    }
    cout << endl;
}

int binarySearch(int arr[], int l, int r, int x)
{
    if (r >= l)
    {
        int mid = l + (r - l) / 2;
 
        if (arr[mid] == x)
            return mid;
 
        if (arr[mid] > x)
            return binarySearch(arr, l, mid - 1, x);
 
        return binarySearch(arr, mid + 1, r, x);
    }
    return l;
}

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;
}