#include <bits/stdc++.h>
using namespace std;
#define FOR(i, j, k) for(int i=(j); i<=(k); i++)
#define FFOR(i, j, k) for(int i=(j); i<(k); i++)
#define DFOR(i, j, k) for(int i=(j); i>=(k); i--)
#define bug(x) cerr<<#x<<" = "<<(x)<<'\n'
#define pb push_back
#define mp make_pair
#define bit(s, i) (((s)>>(i))&1LL)
#define mask(i) ((1LL<<(i)))
#define builtin_popcount __builtin_popcountll
#define __builtin_popcount __builtin_popcountll
using ll=long long; using ld=long double;
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count()); const ld pi=acos(0)*2;
template <typename T> inline void read(T &x){char c; bool nega=0; while((!isdigit(c=getchar()))&&(c!='-')); if(c=='-'){nega=1; c=getchar();} x=c-48; while(isdigit(c=getchar())) x=x*10+c-48; if(nega) x=-x;}
template <typename T> inline void writep(T x){if(x>9) writep(x/10); putchar(x%10+48);}
template <typename T> inline void write(T x){if(x<0){ putchar('-'); x=-x;} writep(x);}
template <typename T> inline void writeln(T x){write(x); putchar('\n');}
#define taskname "Exhibition"
int n, m;
class picture{
public:
int s, v;
void input(){
read(s);
read(v);
}
};
deque <picture> q;
deque <int> c;
int main(){
#ifdef Aria
if(fopen(taskname".in", "r"))
freopen(taskname".in", "r", stdin);
#endif // Aria
read(n);
read(m);
q.resize(n);
c.resize(m);
for(auto &x: q) x.input();
for(auto &x: c) read(x);
sort(c.begin(), c.end());
reverse(c.begin(), c.end());
sort(q.begin(), q.end(), [](picture A, picture B){
return (A.v>B.v)||(A.v==B.v&&A.s>B.s);
});
int ans=0;
while(!(c.empty()||q.empty())){
if(q.front().s>c.front()) q.pop_front();
else{
ans++;
c.pop_front();
q.pop_front();
}
}
writeln(ans);
}
