#include<iostream>
#include<algorithm>
#include<utility>
#include<vector>
using namespace std;
typedef long long ll;
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
int n, m;
cin >> n >> m;
vector<pair<int, int>> vec(n);
for(int i = 0; i < n; i++) cin >> vec[i].second >> vec[i].first;
sort(vec.begin(), vec.end());
vector<int> fr(m);
for(int i = 0; i < m; i++) cin >> fr[i];
sort(fr.begin(), fr.end());
int l = 0, r = min(n, m);
while(l < r){
int mid = ((l + r) >> 1) + 1;
int ptr = m - mid;
for(auto &[val, sz]: vec){
if(ptr < m && sz <= fr[ptr]) ptr++;
}
if(ptr == m) l = mid;
else r = mid - 1;
}
cout << l << "\n";
}
// g++ -std=c++17 -Wall -Wextra -Wshadow -fsanitize=undefined -fsanitize=address -o run pB.cpp
