#include<bits/stdc++.h>
#define ll long long int
#define pb push_back
#define mp make_pair
#define FOR(i,n) for(i=0;i<(n);i++)
#define FORe(i,n) for(i=1;i<=(n);i++)
#define FORr(i,a,b) for(i=(a);i<(b);i++)
#define ii pair<ll,ll>
#define vi vector<ll>
#define vii vector<ii>
#define ff first
#define ss second
#define cd complex<double>
#define vcd vector<cd>
#define ldd long double
#define all(x) (x).begin(),(x).end()
using namespace std;
const short int __PRECISION = 10;
const ll MOD = 1e9+7;
const ll INF = 1e17 + 1101;
const ll LOGN = 17;
const ll MAXN = 2e5+5;
const ll ROOTN = 320;
const ldd PI = acos(-1);
const ldd EPS = 1e-7;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
ll N,M,i,j,k,ans = 0;
cin>>N>>M;
ll C[M];
ii P[N];
FOR(i,N)
{
cin>>j>>k;
P[i] = mp(k,j);
}
FOR(i,M)
cin>>C[i];
sort(C,C+M);
sort(P,P+N);
j = M-1;
i = N-1;
while(j>=0 and i>=0)
{
if(C[j] >= P[i].ss)
{
ans++;
j--;
i--;
}
else
i--;
}
cout<<ans<<endl;
return 0;
}
