#include <bits/stdc++.h>
using namespace std;
const long long INFll = (long long) 1e18 + 10;
const int INFii = (int) 1e9 + 10;
typedef long long ll;
typedef int ii;
typedef long double dbl;
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()
#define maxn 1010
ii n, m, dp[maxn][maxn], c[maxn];
pair<ii,ii> p[maxn];
ii sol(ii i, ii j) {
if(i == n+1 || j == m+1) return 0;
if(dp[i][j] != -1) return dp[i][j];
ii ans = 0;
ans = max(ans,sol(i+1,j));
ans = max(ans,sol(i,j+1));
if(p[i].sc <= c[j]) {
ans = max(ans,sol(i+1,j+1)+1);
}
return dp[i][j] = ans;
}
int main() {
ios::sync_with_stdio(false); cin.tie(0);
//freopen("in.in", "r", stdin);
//freopen("out.out", "w", stdout);
cin >> n >> m;
for(ii i = 1; i <= n; i++) {
cin >> p[i].sc >> p[i].fr;
}
for(ii i = 1; i <= m; i++) {
cin >> c[i];
}
for(ii i = 1; i <= n; i++) {
for(ii j = 1; j <= m; j++) {
dp[i][j] = -1;
}
}
sort(p+1,p+1+n);
sort(c+1,c+1+m);
cout << sol(1,1) << endl;
}
