#include<cstdio>

#include<iostream>

#include<cstring>

using namespace std;

//你弱，有什么资格休息

#define ull unsigned long long

#define ll long long

#define R register ll

#define pause (for(R i=1;i<=10000000000;++i))

#define In freopen("NOIPAK++.in","r",stdin)

#define Out freopen("out.out","w",stdout)

namespace Fread {

static char B[<<],*S=B,*D=B;

#ifndef JACK

#define getchar() (S==D&&(D=(S=B)+fread(B,1,1<<15,stdin),S==D)?EOF:*S++)

#endif

inline int g() {

    R ret=,fix=; register char ch; while(!isdigit(ch=getchar())) fix=ch=='-'?-:fix;

    if(ch==EOF) return EOF; do ret=ret*+(ch^); while(isdigit(ch=getchar())); return ret*fix;

} inline bool isempty(const char& ch) {return (ch<=||ch>=);}

inline void gs(char* s) {

    register char ch; while(isempty(ch=getchar()));

    do *s++=ch; while(!isempty(ch=getchar()));

}

} using Fread::g; using Fread::gs;

namespace Luitaryi {

const int N=1e++;

int n,m,ans=-,cnt;

int a[N],w[N];

bool vis[N],flg[N];

inline bool ck(int x) { R ret=,tmp=m;

    memset(vis,,sizeof(vis)); memset(flg,,sizeof(flg));

    for(R i=x;i>=&&tmp;--i) if(a[i]&&!vis[a[i]]) vis[a[i]]=true,flg[i]=true,--tmp;

    if(tmp!=) return false;

    for(R i=;i<=x;++i) {

        if(a[i]!=&&flg[i]) ret-=w[a[i]];

        else ++ret;

        if(ret<) return false;

    } return ret>=;

}

inline void main() {

    n=g(),m=g();

    for(R i=;i<=n;++i) a[i]=g();

    for(R i=;i<=m;++i) w[i]=g();

    R l=m,r=n+; while(l<r) {

        R md=l+r>>;

        if(ck(md)) r=md;

        else l=md+;

    } printf("%d\n",l==n+?-:l);

}

}

signed main() {

    Luitaryi::main();

    return ;

}