#include<iostream>
#include<bits/stdc++.h>
using namespace std;
int n,m,ans,a[301000],p;
int main()
{
    //freopen("kra.in","r",stdin);
    //freopen("kra.out","w",stdout);
    int n,m;
    cin>>n>>m;
    for(int i=1; i<=n; i++) scanf("%d",&a[i]);
    for(int i=2; i<=n; i++) if(a[i]>a[i-1]) a[i]=a[i-1];
    ans=n+1;
    for(int i=1; i<=m; i++)
    {
        scanf("%d",&p);
        int l=1,r=ans-1,t;
        while(l<=r)
        {
            int mid=(l+r)>>1;
            if(a[mid]>=p) {t=mid;l=mid+1;}
            else r=mid-1;
        }
        ans=t;
        if(ans<=0)
        {
            cout<<'0'<<endl;
            return 0;
        }
    }
    cout<<ans<<endl;
    return 0;
}