#include <bits/stdc++.h>   using namespace std;   int a[100500];   int sp[2005];   int f[100500], l[100500];   int n, m;   int ns[2 * 100500];   int ps[2 * 100500];   int used[2 * 100500];   int lp[100500];   int rp[100500];   int main() {     scanf( %d%d , &n, &m);     for (int i = 1; i <= n; ++i) {       scanf( %d , a + i);     }     sort(a + 1, a + n + 1);     for (int i = 1; i <= m; ++i) {       scanf( %d , sp + i);       used[sp[i]] = true;       ns[sp[i]] = sp[i];       ps[sp[i]] = sp[i];     }     for (int i = n; i >= 1; --i) {       if (i != n && a[i] == a[i + 1] - 1) {         rp[i] = rp[i + 1];       } else {         rp[i] = i;       }     }     for (int i = 1; i <= n; ++i) {       if (i != 1 && a[i] == a[i - 1] + 1) {         lp[i] = lp[i - 1];       } else {         lp[i] = i;       }     }     for (int i = 2 * 100500 - 2; i >= 0; --i) {       if (ns[i] == 0) {         ns[i] = ns[i + 1];       }     }     for (int i = 1; i < 2 * 100500; ++i) {       if (ps[i] == 0) {         ps[i] = ps[i - 1];       }     }     sort(sp + 1, sp + m + 1);     f[0] = 0, l[0] = 0;     for (int i = 1; i <= n; ++i) {       int df = a[i] - i;       for (int cp = a[i], cnt = used[a[i]]; cp && df < cp;            ++cnt, cp = ps[cp - 1]) {         l[i] = max(l[i], f[lp[i - a[i] + cp] - 1] + cnt);       }       f[i] = max(f[i], l[i]);       df = n - i + a[i];       for (int cp = a[i], cnt = used[a[i]]; cp && df >= cp;            ++cnt, cp = ns[cp + 1]) {         f[rp[i + cp - a[i]]] = max(f[rp[i + cp - a[i]]], l[i] + cnt - used[a[i]]);       }     }     int res = *max_element(f + 1, f + n + 1);     printf( %d n , res);     return 0;   }   