#include <bits/stdc++.h>
using namespace std;
struct Data {
int Size, val;
bool operator < (const Data &other) const {
if (Size != other.Size) return Size < other.Size;
return val < other.val;
}
};
int numPic, numFrame;
#define MAX_N 100100
Data a[MAX_N];
int frame[MAX_N];
struct Fenwick {
int bit[MAX_N];
void update(int x, int v) {
for (; x <= numPic; x += x & (-x)) bit[x] = max(bit[x], v);
}
int get(int x) {
int ans = 0;
for (; x > 0; x -= x & (-x)) ans = max(ans, bit[x]);
return ans;
}
} maxTree;
bool check(int val) {
for (int i = 1; i <= numPic; ++i) maxTree.bit[i] = 0; // reset;
for (int i = 1; i <= numPic; ++i) {
int cur = maxTree.get(a[i].val);
if (cur == val) return true;
assert(numFrame - val + cur + 1 <= numFrame);
if (frame[numFrame - val + cur + 1] >= a[i].Size) {
maxTree.update(a[i].val, cur + 1);
if (cur + 1 == val) return true;
}
}
return false;
}
int main() {
ios_base::sync_with_stdio(false);cin.tie(nullptr);
cin >> numPic >> numFrame;
for (int i = 1; i <= numPic; ++i) cin >> a[i].Size >> a[i].val;
for (int i = 1; i <= numFrame; ++i) cin >> frame[i];
sort(a + 1, a + 1 + numPic);
sort(frame + 1, frame + 1 + numFrame);
vector<int> compressed;
for (int i = 1; i <= numPic; ++i) compressed.push_back(a[i].val);
sort(compressed.begin(), compressed.end());
compressed.resize(unique(compressed.begin(), compressed.end()) - compressed.begin());
for (int i = 1; i <= numPic; ++i) a[i].val = upper_bound(compressed.begin(), compressed.end(), a[i].val) - compressed.begin();
int l = 1, r = min(numPic, numFrame), g, vt = 0;
while (l <= r) {
g = (l + r) >> 1;
if (check(g)) vt = g, l = g + 1;
else r = g - 1;
}
cout << vt;
return 0;
}
