#include <bits/stdc++.h>
#define pb push_back
#define endl ("\n")
#define all(aa) aa.begin(), aa.end()
typedef long long ll;
using namespace std;
struct segTree{
int n;
vector<int> t;
segTree(int n) : n(n), t(4 * n, INT_MAX){}
void upd(int u, int tl, int tr, int pos, int val){
if(tl == tr){
t[u] = val;
return;
}
int tm = (tl + tr) / 2;
if(pos <= tm)
upd(u * 2, tl, tm, pos, val);
else
upd(u * 2 + 1, tm + 1, tr, pos, val);
t[u] = min(t[u * 2], t[u * 2 + 1]);
}
void upd(int pos, int val){
upd(1, 0, n - 1, pos, val);
}
int walk(int u, int tl, int tr, int x){
if(tl == tr){
return tl;
}
int tm = (tl + tr) / 2;
if(t[u * 2 + 1] <= x)
return walk(u * 2 + 1, tm + 1, tr, x);
return walk(u * 2, tl, tm, x);
}
int walk(int x){
return walk(1, 0, n - 1, x);
}
};
int main(){
int n, m;
cin >> n >> m;
vector<array<int, 2>> a(n);
vector<int> c(m);
for(int i = 0; i < n; i++) cin >> a[i][1] >> a[i][0];
for(int i = 0; i < m; i++) cin >> c[i];
sort(all(a));
segTree st(n);
for(int i = 0; i < n; i++){
st.upd(i, a[i][1]);
}
sort(all(c));
int ans = 0;
int r = n;
for(int i = m - 1; i >= 0; i--){
int j = st.walk(c[i]);
if(a[j][1] > c[i]) continue;
while(j < r){
r--;
st.upd(r, INT_MAX);
}
ans++;
}
cout << ans << endl;
}
