#include <bits/stdc++.h>
#define all(x) (x).begin(), (x).end()
#define gc getchar()
#define pc(x) putchar(x)
template<typename T> void scan(T &x){x = 0;bool _=0;T c=gc;_=c==45;c=_?gc:c;while(c<48||c>57)c=gc;for(;c<48||c>57;c=gc);for(;c>47&&c<58;c=gc)x=(x<<3)+(x<<1)+(c&15);x=_?-x:x;}
template<typename T> void printn(T n){bool _=0;_=n<0;n=_?-n:n;char snum[65];int i=0;do{snum[i++]=char(n%10+48);n/= 10;}while(n);--i;if (_)pc(45);while(i>=0)pc(snum[i--]);}
template<typename First, typename ... Ints> void scan(First &arg, Ints&... rest){scan(arg);scan(rest...);}
template<typename T> void print(T n){printn(n);pc(10);}
template<typename First, typename ... Ints> void print(First arg, Ints... rest){printn(arg);pc(32);print(rest...);}
using namespace std;
const int MM = 1e5+5;
int n, m;
pair<int, int> a[MM];
int b[MM], ans;
multiset<int> st;
int main(){
scan(n, m);
for(int i = 0; i < n; i++)
scan(a[i].second, a[i].first);
sort(a, a+n);
for(int i = 0; i < m; i++){
scan(b[i]);
st.insert(b[i]);
}
for(int i = n-1; i >= 0; i--){
if(size(st) and a[i].second <= *--st.end()){
st.erase(--st.end());
ans++;
}
}
print(ans);
}
