#include <bits/stdc++.h>

using namespace std;

const int mod = 1e9 + 7;

int n, m, i, j, q, sc, ans;
int f[2002][2005];
int s[2002 * 2002];
int fwt[2002 * 2002];
int la[2002 * 2002];
int a[2002], b[2002];

inline int access(int x) {
    if (la[x] < q) return 0;
    return fwt[x];
}

inline int compress(int x) {
    return (lower_bound(s + 1, s + sc + 1, x) - (s + 1)) + 2;
}

inline void modify(int x, int v) {
    for (; x <= sc + 4; x = (x | (x - 1)) + 1) {
        fwt[x] = (access(x) + v) % mod;
        la[x] = q;
    }
}
inline int findsum(int x) {
    int s = 0;
    for (; x; x &= (x - 1)) {
        s = (s + access(x)) % mod;
    }
    return s;
}

int main() {
    //freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; i++) scanf("%d", a + i);
    for (int i = 1; i <= m; i++) scanf("%d", b + i);
    q++;
    for (int i = 1; i <= n; i++) f[i][1] = 1;
    for (int i = 2; i <= m; i++) {
        sc = 0;
        for (int j = 1; j <= n; j++) s[++sc] = a[j] + b[i - 1];
        for (int j = 1; j <= n; j++) s[++sc] = a[j] + b[i];
        sort(s + 1, s + sc + 1);
        q++;
        for (int j = 1; j <= n; j++) {
            f[j][i] = findsum(compress(a[j] + b[i]));
            modify(compress(a[j] + b[i - 1]), f[j][i - 1]);
        }
    }
    ans = 0;
    for (int i = 1; i <= n; i++) ans = (ans + f[i][m]) % mod;
    printf("%d\n", ans);
    return 0;
}