noname64

int n = readint(), m = readint();
pair<int, int> a[100001];

int main(){
    FOR(i, 1, n + 1) a[readint()].fus = i;
    FOR(i, 1, m + 1) a[i].sec = readint();
    sort(a + 1, a + m + 1);
    int res = a[1].sec + 1, d = a[1].fus - a[1].sec - 1;
    if(d < 0) return cout << -1, 0;
    FOR(i, 2, m + 1){
        res += a[i].sec + 1,
        d += a[i].fus - a[i - 1].fus - a[i].sec - 1;
        if(d < 0) return cout << -1, 0;
    }
    return cout << res, 0;
}