#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <queue>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <memory.h>
#include <ctime>
#include <bitset>
#include <unordered_map>

using namespace std;

#define ABS(a) ((a>0)?a:-(a))
#define MIN(a,b) ((a<b)?(a):(b))
#define MAX(a,b) ((a<b)?(b):(a))
#define FOR(i,a,n) for (int i=(a);i<(n);++i)
#define FI(i,n) for (int i=0; i<(n); ++i)
#define pnt pair <int, int>
#define mp make_pair
#define PI 3.1415926535897
#define MEMS(a,b) memset(a,b,sizeof(a))
#define LL long long
#define U unsigned

vector<int> a,b;
vector<int> c;

int main()
{
#ifdef Fcdkbear
    freopen("in.txt", "r", stdin);
    double beg = clock();
    //freopen("out.txt", "w", stdout);
#endif

    int n,m;
    scanf("%d%d",&n,&m);
    a.resize(n);
    b.resize(m);
    FOR(i,0,n)
        scanf("%d",&a[i]);
    FOR(i,0,m)
        scanf("%d",&b[i]);
    sort(a.rbegin(), a.rend());
    sort(b.rbegin(), b.rend());
    int res = 0;
    int l = 1, r = m;
    while (l<=r)
    {
        int mid = (l+r) / 2;
        c.clear();
        for (int i = mid - 1; i >= 0; --i)
            c.push_back(b[i]);
        LL have1 = 1;
        LL have2 = 0;
        int lev = 0;
        int p1 = 0;
        int p2 = 0;
        bool f = true;
        while (1)
        {
            while ((p1<c.size()) && (c[p1] == lev) && (have1>0))
            {
                have1--;
                p1++;
            }
            if (p1 == c.size())
                break;
            if (have1 == 0)
            {
                f = false;
                break;
            }
            while ((have1) && (p2 < a.size()))
            {
                have1--;
                have2+=a[p2];
                p2++;
            }
            if (p2 == a.size())
            {
                if (have1+have2<(int)c.size() - p1)
                    f = false;
                break;
            }
            have1 = have2;
            have2 = 0;
            lev++;
        }
        if (f)
        {
            res = mid;
            l = mid + 1;
        }
        else
            r = mid - 1;
    }
    cout<<res<<endl;



#ifdef Fcdkbear
    double end = clock();
    fprintf(stderr, "*** Total time = %.3lf ***\n", (end - beg) / CLOCKS_PER_SEC);
#endif
    return 0;
}