#include <bits/stdc++.h>
using namespace std;
struct pos
{
int val, s;
bool operator<(pos b)
{
if(val != b.val)
return val<b.val;
return s < b.s;
}
};
int n,m;
pos v[100005];
int s[100005];
int dp[100005];
int cbDp(int val)
{
for(int i=n;i>=0;i--)
if(dp[i] <= val)
return i;
return n+1;
/*
int st=0, dr=n, mij, last=n+1;
while(st <= dr)
{
mij = (st+dr)/2;
if(dp[mij] <= val)
{
last=mij;
st=mij+1;
}
else
dr=mij-1;
}
return last;
*/
}
int cbS(int val)
{
for(int i=1;i<=m;i++)
if(s[i] >= val)
return i;
return m+1;
/*
int st=1, dr=m, mij, last=m+1;
while(st <= dr)
{
mij=(st+dr)/2;
if(s[mij] <= val)
{
last=mij;
dr=mij-1;
}
else
st=mij+1;
}
return last;
*/
}
int main()
{
cin>>n>>m;
for(int i=1;i<=n;i++)
cin>>v[i].s>>v[i].val;
sort(v+1, v+n+1);
for(int i=1;i<=m;i++)
cin>>s[i];
sort(s+1, s+m+1);
for(int i=1;i<=n;i++)
dp[i] = 1e9;
for(int i=1;i<=n;i++)
{
if(v[i].s > s[m])
continue;
for(int j=n-1;j>=0;j--)
{
int sId = max(dp[j]+1, cbS(v[i].s));
if(sId <= m)
dp[j+1] = min(dp[j+1], sId);
}
/*
for(int j=0;j<=n;j++)
cout<<dp[j]<<' ';
cout<<'\n';
*/
}
int ans=0;
for(int i=1;i<=n;i++)
if(dp[i] != 1e9)
ans = max(ans, i);
cout<<ans;
return 0;
}
