#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define REP(i,n) for(int i=0;i<n;++i)
#define REP1(i,n) for(int i=1;i<=n;++i)
#define SZ(i) int(i.size())
#define eb emplace_back
#define ALL(i) i.begin(),i.end()
#define X first
#define Y second
#ifdef tmd
#define IOS()
#define debug(...) fprintf(stderr,"#%d: %s = ",__LINE__,#__VA_ARGS__),_do(__VA_ARGS__);
template<typename T> void _do(T &&x){cerr<<x<<endl;}
template<typename T, typename ...S> void _do(T &&x, S &&...y){cerr<<x<<", ";_do(y...);}
template<typename It> ostream& _printRng(ostream &os,It bg,It ed)
{
os<<"{";
for(It it=bg;it!=ed;it++) {
os<<(it==bg?"":",")<<*it;
}
os<<"}";
return os;
}
template<typename T> ostream &operator << (ostream &os,vector<T> &v){return _printRng(os,v.begin(), v.end());}
template<typename T> void pary(T bg, T ed){_printRng(cerr,bg,ed);cerr<<endl;}
#else
#define IOS() ios_base::sync_with_stdio(0);cin.tie(0);
#define endl '\n'
#define debug(...)
#define pary(...)
#endif
const int MAXN = 100005;
const ll MOD = 1000000007;
int n, m;
vector<pii> paint;
vector<int> frame;
/*********************GoodLuck***********************/
int main () {
IOS();
cin >> n >> m;
REP (i, n) {
int s, v;
cin >> s >> v;
paint.emplace_back(v, s);
}
sort(ALL(paint));
REP (i, m) {
int s;
cin >> s;
frame.emplace_back(s);
}
sort(ALL(frame));
reverse(ALL(paint));
int idx = SZ(frame) - 1, ans = 0;
for (auto v : paint) {
if (idx >= 0 && v.Y <= frame[idx]) {
ans++;
idx--;
}
}
cout << ans << endl;
}
