1 #include <iostream>
 2 #include <queue>
 3 #include <stack>
 4 #include <cstdio>
 5 #include <vector>
 6 #include <map>
 7 #include <set>
 8 #include <bitset>
 9 #include <algorithm>
10 #include <cmath>
11 #include <cstring>
12 #include <cstdlib>
13 #include <string>
14 #include <sstream>
15 #include <time.h>
16 #define x first
17 #define y second
18 #define pb push_back
19 #define mp make_pair
20 #define lson l,m,rt*2
21 #define rson m+1,r,rt*2+1
22 #define mt(A,B) memset(A,B,sizeof(A))
23 #define mod 1000000007
24 using namespace std;
25 typedef long long LL;
26 const double PI = acos(-1);
27 const int N=1e5+10;
28 const int inf = 0x3f3f3f3f;
29 const LL INF=0x3f3f3f3f3f3f3f3fLL;
30 int w[N],D[N];
31 int main()
32 {
33 #ifdef Local
34     freopen("data.txt","r",stdin);
35 #endif
36     int n,m,ans=0;
37     cin>>n>>m;
38     for(int i=0;i<n;i++)cin>>w[i];
39     for(int i=0;i<m;i++)cin>>D[i];
40     for(int i=1;i<n;i++)
41     {
42         if(w[i]>w[i-1])w[i]=w[i-1];
43     }
44     sort(w,w+n);
45     w[n]=inf;
46     for(int i=0,k=0;i<m;i++)
47     {
48         k=lower_bound(w+k,w+n+1,D[i])-w+1;
49         if(k>n)break;
50         ans++;
51     }
52     cout<<ans<<endl;
53 #ifdef Local
54     cerr << "time: " << (LL) clock() * 1000 / CLOCKS_PER_SEC << " ms" << endl;
55 #endif
56 }