#include <fstream>
#include <algorithm>

using namespace std;

ifstream fin("info.in");
ofstream fout("info.out");

#define DIM 100000

int n, m;
int f[DIM + 1], b[DIM + 1];

int main() {
  fin >> n >> m;
  for(int i = 1; i <= n; i++)
    fin >> f[i];
  for(int i = 1; i <= n; i++)
    fin >> b[i];
  
  sort(f + 1, f + n + 1);
  sort(b + 1, b + m + 1);

  b[m + 1] = 2e9; //santinela;
  int j = 1, cupluri = 0;
  for(int i = 1; i <= n; i++) {
    while(f[i] > b[j])  //caut un baiat compatibil;
      j++;
    if(j <= n) {
      cupluri++;
      j++;        //baiatul actual are pereche;
    }
  }
  fout << cupluri;

  return 0;
}