#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define f first
#define s second
#define ii pair <int,int>
#define pii pair <ll,ll>
const int N = 1e5;
const int MOD = 1e9 + 7;
const ll oo = 1e18;
ii a[N + 5];
int c[N + 5],n,m;
bool ok(int x)
{
priority_queue <int, vector <int>, greater <int>> pq;
int j = 1, tmp = 0;
for (int i = x; i <= m; ++i) {
while (j <= n && c[i] >= a[j].f) {
if (a[j].s >= tmp) pq.push(a[j].s);
++j;
}
if (pq.empty()) return false;
tmp = pq.top();
pq.pop();
}
return true;
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n >> m;
for (int i = 1; i <= n; ++i) {
cin >> a[i].f >> a[i].s;
}
for (int i = 1; i <= m; ++i) cin >> c[i];
sort(a + 1, a + 1 + n);
sort(c + 1, c + 1 + m);
for (int i = 1; i <= m; ++i) {
if (ok(i)) {
cout << m - i + 1 << '\n';
return 0;
}
}
cout << 0;
}
