#include <bits/stdc++.h>
using namespace std;
using ll = long long;
struct SegTree {
int n;
vector<int> st;
SegTree() { n = 0; }
SegTree(int _n) { init(_n); }
void init(int _n) {
n = 1;
while (n < _n) n <<= 1;
st.assign(2*n, 0);
}
// add v at position p (0-based)
void add(int p, int v) {
p += n;
st[p] += v;
p >>= 1;
while (p) {
st[p] = st[p<<1] + st[p<<1|1];
p >>= 1;
}
}
// query sum on [l,r] inclusive
int sum_range(int l, int r) {
if (l > r) return 0;
l += n; r += n;
int res = 0;
while (l <= r) {
if (l & 1) res += st[l++];
if (!(r & 1)) res += st[r--];
l >>= 1; r >>= 1;
}
return res;
}
// find first index >= ql with count > 0, or -1 if none
int find_first_ge(int ql) {
if (ql >= n) return -1;
// if no elements in [ql, n-1] return -1
if (sum_range(ql, n-1) == 0) return -1;
int node = 1, l = 0, r = n-1;
// descend but skip left parts that are entirely before ql
while (l != r) {
int mid = (l + r) >> 1;
int leftNode = node<<1;
if (ql <= mid) {
// left side may contain answer
if (st[leftNode] > 0) {
node = leftNode;
r = mid;
} else {
node = leftNode|1;
l = mid+1;
}
} else {
// skip left entirely
node = leftNode|1;
l = mid+1;
}
}
return (l < n) ? l : -1;
}
};
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int N, M;
if (!(cin >> N >> M)) return 0;
vector<pair<ll,ll>> pics(N); // (value, size)
for (int i = 0; i < N; ++i) {
ll S, V; cin >> S >> V;
pics[i] = {V, S};
}
vector<ll> frames(M);
for (int j = 0; j < M; ++j) cin >> frames[j];
// ordenar imágenes por valor asc, y para igual valor por tamaño desc
sort(pics.begin(), pics.end(), [](const pair<ll,ll>& a, const pair<ll,ll>& b){
if (a.first != b.first) return a.first < b.first;
return a.second > b.second;
});
// compresión de tamaños (tanto de imágenes como de marcos)
vector<ll> all;
all.reserve(N + M);
for (auto &pv : pics) all.push_back(pv.second);
for (ll c : frames) all.push_back(c);
sort(all.begin(), all.end());
all.erase(unique(all.begin(), all.end()), all.end());
auto comp = [&](ll x)->int {
return int(lower_bound(all.begin(), all.end(), x) - all.begin());
};
int C = (int)all.size();
// construir segment tree con conteos de marcos por tamaño comprimido
SegTree st(C);
for (ll c : frames) {
int idx = comp(c);
st.add(idx, 1);
}
int ans = 0;
for (auto &pv : pics) {
ll need_size = pv.second;
int need_idx = comp(need_size);
// buscamos primer índice >= need_idx con count>0
int pos = st.find_first_ge(need_idx);
if (pos != -1 && pos < C) {
// asignar ese marco (decrementar)
st.add(pos, -1);
++ans;
}
}
cout << ans << "\n";
return 0;
}
