#include<cstdio>

#include<cctype>

#include<map>

#include<algorithm>

using namespace std;

map<int,int> vis;

inline long long read(){

    long long num=,f=;

    char ch=getchar();

    while(!isdigit(ch)){

        if(ch=='-')    f=-;

        ch=getchar();

    }

    while(isdigit(ch)){

        num=num*+ch-'';

        ch=getchar();

    }

    return num*f;

}

int a[];

int b[];

int sot[];

int f[];

int size;

int cnt;

int check(int s){

    int l=,r=cnt;

    while(l<=r){

        int mid=(l+r)>>;

        if(f[mid]==s)    return mid;

        if(f[mid]<s)    l=mid+;

        if(f[mid]>s)    r=mid-;

    }

    return l;

}

int main(){

    int n=read(),m=read();

    for(int i=;i<=n;++i)    a[i]=read();

    for(int i=;i<=m;++i)    b[i]=read();

    for(int i=;i<=n;++i)    vis[a[i]]=i;

    for(int i=;i<=m;++i){

        int S=vis[b[i]];

        if(S>)        b[i]=S;

        else b[i]=0x7fffffff;

    }

    for(int i=;i<=m;++i){

        if(b[i]==0x7fffffff)    continue;

        int pos=check(b[i]);

        f[pos]=b[i];

        cnt=cnt<pos?pos:cnt;

    }

    printf("%d",cnt);

    return ;

}