#include <iostream>
#include <algorithm>
#include <vector>
#include <random>
#include <chrono>
#include <set>
#include <map>
#include <stack>
#include <functional>
#include <iomanip>
#include <queue>
#include <cassert>
#include <complex>
#include <cstring>
#include <memory>
#include <bitset>
#include <sstream>
#include <cmath>
#include <numeric>
#include <numbers>
#include <fstream>
using namespace std;
#ifndef template
#ifndef define
#define ll long long
#define ld long double
#define pl pair<ll, ll>
#define pi pair<int, int>
#define nl cout << '\n';
#define x first
#define y second
#define cbit(x) __builtin_popcountll(x)
#define uid(a, b) uniform_int_distribution<ll>(a, b)(rng)
#define siz(x) (int)x.size()
#endif
#ifndef print
void print(size_t x) {cout << x << ' ';}
void print(int x) {cout << x << ' ';}
void print(long long x) {cout << x << ' ';}
void print(float x) {cout << x << ' ';}
void print(long double x) {cout << x << ' ';}
void print(char x) {cout << x << ' ';}
void print(const char* x) {cout << x << ' ';}
void print(bool x) {cout << x << ' ';}
void print(string &x) {cout << x << ' ';}
template<typename T, typename V>
void print(pair<T, V> &p) {print(p.x); print(p.y);}
template<typename T>
void print(vector<T> v) {for (int i = 0; i < v.size(); i++) print(v[i]);}
template<typename T>
void print(vector<vector<T>> v) {
for (int i = 0; i < v.size(); i++){
for (int j = 0; j < v[i].size(); j++)
print(v[i][j]);
nl;
}
}
template <typename T, typename... V>
void print(T t, V&&... v) {print(t); print(v...);}
#endif
#ifndef read
void read(int &x) {cin >> x;}
void read(long long &x) {cin >> x;}
void read(unsigned &x) {cin >> x;}
void read(unsigned long long &x) {cin >> x;}
void read(float &x) {cin >> x;}
void read(long double &x) {cin >> x;}
void read(char &x) {cin >> x;}
void read(string &x) {cin >> x;}
void read(bool &x) {cin >> x;}
template<typename T>
void read(vector<T> &v) {
for (int i = 0; i < v.size(); i++)
read(v[i]);
}
template <typename T, typename... V>
void read(T &t, V&... v) {read(t); read(v...);}
#endif
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
template<class T> bool maxi(T& a, const T& b) {
return a < b ? a = b, 1 : 0;
}
template<class T> bool mini(T& a, const T& b) {
return a > b ? a = b, 1 : 0;
}
template<class... Args>
auto vec(size_t n, Args&&... args) {
if constexpr(sizeof...(args) == 1)
return vector(n, args...);
else
return vector(n, vec(args...));
}
#endif
using namespace std;
const ll inf = 1e18;
const ll def = 1e5+1;
const ll mod = 1e9;
template<typename T>
struct SegmentTreeFast{
vector<T> a;
T defv;
int n;
SegmentTreeFast(int n, T defv) : n(n), defv(defv){
a = vector<T>(2 * n, defv);
}
T cmb(T a, T b){ //change if needed
return max(a, b);
}
void build(){ //array is at i + n index
for (int i = n - 1; i > 0; --i)
a[i] = cmb(a[i << 1], a[i << 1 | 1]);
}
void update(int i, T v){
T val = a[i + n];
for (a[i += n] = cmb(v, val); i > 1; i >>= 1)
a[i >> 1] = cmb(a[i], a[i ^ 1]);
}
T get(int l, int r){
r++;
T res = defv;
for (l += n, r += n; l < r; l >>= 1, r >>= 1){
if (l&1) res = cmb(res, a[l++]);
if (r&1) res = cmb(res, a[--r]);
}
return res;
}
};
void solve(){
int n, m;
read(n, m);
vector<pl> p(n);
for (int i = 0; i < n; i++)
read(p[i].y, p[i].x);
auto c = vec(m, 0ll);
read(c);
sort(p.begin(), p.end());
auto dp = vec(n, 0);
SegmentTreeFast<int> st(m, 0);
sort(c.begin(), c.end());
for (int i = n - 1; i >= 0; i--){
int u = lower_bound(c.begin(), c.end(), p[i].y) - c.begin();
if (u == m)
continue;
int val = st.get(u, m - 1) + 1;
dp[i] = min(val, m - u);
st.update(u, dp[i]);
}
int res = *max_element(dp.begin(), dp.end());
print(res);
}
/*
*/
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
if (ifstream("input.txt").good()){
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
}
int t;
t = 1;
while (t--){
solve();
nl;
}
}
