#include <bits/stdc++.h>
using namespace std;
#define int long long
#define FOR(I, L, R) for(int I(L) ; I <= (int)R ; ++I)
#define FOD(I, R, L) for(int I(R) ; I >= (int)L ; --I)
#define FOA(I, A) for(auto &I : A)
#define print(A,L,R) FOR(OK, L, R){if(A[OK]<=-oo / 10||A[OK]>=oo)cout<<"- ";else cout<<A[OK]<<' ';}cout<<'\n';
#define prints(A) FOA(OK, A){cout<<OK<<' ';}cout << '\n';
#define printz(A,L,R) FOR(OK, 1, L){FOR(KO, 1, R){if(A[OK][KO]>-oo&&A[OK][KO]<oo)cout<<A[OK][KO]<<' ';else cout << "- ";} cout << '\n';}cout << '\n';
#define fs first
#define sd second
#define ii pair<int,int>
#define iii pair<int, ii>
#define all(A) A.begin(), A.end()
#define quickly cin.tie(0) -> ios_base::sync_with_stdio(0);
const int N = 2e5 + 5;
const int mod = 1e9 + 7;
const int oo = 1e9;
int n, m;
ii a[N];
int w[N];
bool calc(int x){
int cnt = 1;
FOD(i, n, 1){
if(a[i].sd <= w[cnt]){
++cnt;
}
if(cnt == x + 1) return 1;
}
return 0;
}
signed main(){ quickly
cin >> n >> m;
FOR(i, 1, n){
cin >> a[i].sd >> a[i].fs;
}
sort(a + 1, a + 1 + n);
FOR(i, 1, m){
cin >> w[i];
}
sort(w + 1, w + 1 + m, greater<int>());
int l = 1, r = min(n, m);
int ans = 0;
while(l <= r){
int mid = (l + r) >> 1;
if(calc(mid)){
l = mid + 1;
ans = mid;
}
else{
r = mid - 1;
}
}
cout << ans;
}
