//#include<bits\stdc++.h>

#include<iostream>

#include<iomanip>

#include<cstdio>

#include<cstring>

#include<string>

#include<ctime>

#include<cmath>

#include<cctype>

#include<cstdlib>

#include<queue>

#include<deque>

#include<stack>

#include<vector>

#include<algorithm>

#include<utility>

#include<bitset>

#include<set>

#include<map>

#define ll long long

#define db double

#define INF 10000000000000000ll

#define ldb long double

#define pb push_back

#define put_(x) printf("%d ",x);

#define get(x) x=read()

#define gt(x) scanf("%d",&x)

#define gi(x) scanf("%lf",&x)

#define put(x) printf("%d\n",x)

#define putl(x) printf("%lld\n",x)

#define gc(a) scanf("%s",a+1)

#define rep(p,n,i) for(RE int i=p;i<=n;++i)

#define go(x) for(int i=lin[x],tn=ver[i];i;tn=ver[i=nex[i]])

#define fep(n,p,i) for(RE int i=n;i>=p;--i)

#define vep(p,n,i) for(RE int i=p;i<n;++i)

#define pii pair<int,int>

#define mk make_pair

#define RE register

#define P 1000000007

#define gf(x) scanf("%lf",&x)

#define pf(x) ((x)*(x))

#define uint unsigned long long

#define ui unsigned

#define EPS 1e-4

#define sq sqrt

#define S second

#define F first

#define mod 1000000007

#define V vector<int>

#define l(x) t[x].l

#define r(x) t[x].r

#define sum(x) t[x].sum

#define cnt(x) t[x].cnt

using namespace std;

char buf[1<<15],*fs,*ft;

inline char getc()

{

    return (fs==ft&&(ft=(fs=buf)+fread(buf,1,1<<15,stdin),fs==ft))?0:*fs++;

}

inline int read()

{

    RE int x=0,f=1;RE char ch=getc();

    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getc();}

    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getc();}

    return x*f;

}

const int MAXN=150010,maxn=40010;

bitset<MAXN>ans,w;

int a[MAXN],b[maxn];

int c[MAXN],p[MAXN];

int n,m;

inline int cmp1(int x,int y){return a[x]>a[y];}

inline int cmp2(int x,int y){return b[x]>b[y];}

int main()

{

	freopen("1.in","r",stdin);

	get(n);get(m);

	rep(1,n,i)get(a[i]),p[i]=i;

	rep(1,m,i)get(b[i]),c[i]=i;

	sort(p+1,p+1+n,cmp1);

	sort(c+1,c+1+m,cmp2);

	int flag=1;

	ans.set();

	rep(1,m,i)

	{

		while(a[p[flag]]>=b[c[i]]&&flag<=n)

		{

			w[p[flag]]=1;

			++flag;

		}

		ans=ans&(w>>c[i]-1);

	}

	put(ans.count());return 0;

}