/*
author : PakinDioxide
created : 29/03/2025 01:59
task : JOI19_ho_t2
*/
#include <bits/stdc++.h>
#define ll long long
using namespace std;
int main() {
ios::sync_with_stdio(0), cin.tie(0);
ll n, m;
cin >> n >> m;
pair <ll, ll> a[n];
ll c[m];
for (auto &[y, x] : a) cin >> x >> y;
for (auto &e : c) cin >> e;
sort(a, a+n);
sort(c, c+m);
ll pos[n];
for (int i = 0; i < n; i++) pos[i] = lower_bound(c, c+m, a[i].second) - c;
ll dp[n], mx = 0;
dp[n-1] = (pos[n-1] < m);
for (int i = n-2; i >= 0; i--) {
dp[i] = 0;
if (pos[i] == m) continue;
for (int j = i+1; j < n; j++) {
if (pos[j] > pos[i]) dp[i] = max(dp[i], dp[j]+1);
else dp[i] = max(dp[i], min(dp[j]+1, m-pos[i]));
}
mx = max(mx, dp[i]);
}
cout << mx << '\n';
}
