#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define fi first
#define se second
const bool Multitest = 0;
const int N = 1e5 + 10;
pair<int, int> a[N]; int b[N];
int n, m;
void maximize(int& a, int b)
{
if(a < b) a = b;
}
namespace sub1
{
const int Nsub = 1e3 + 10;
int dp[Nsub][Nsub];
void solve()
{
sort(a + 1, a + 1 + n);
sort(b + 1, b + 1 + m);
for(int i = 1 ; i <= m ; i++)
{
for(int j = 1 ; j <= n ; j++)
{
dp[i][j] = dp[i - 1][j - 1] + (a[j].se <= b[i]);
maximize(dp[i][j], dp[i][j - 1]);
}
}
cout << dp[m][n];
}
}
namespace sub3
{
int dp[N]; pair<int, int> c[N];
struct ST
{
int t[4 * N];
void update(int id, int l, int r, int u, int v)
{
if(r < u || u < l) return;
if(l == r)
{
t[id] = v;
return;
}
int mid = (l + r) >> 1;
update(id * 2, l, mid, u, v);
update(id * 2 + 1, mid + 1, r, u, v);
t[id] = max(t[id * 2], t[id * 2 + 1]);
}
int get(int id, int l, int r, int u, int v)
{
if(r < u || v < l) return 0;
if(u <= l && r <= v) return t[id];
int mid = (l + r) >> 1;
return max(get(id * 2, l, mid, u, v), get(id * 2 + 1, mid + 1, r, u, v));
}
}; ST st;
void solve()
{
sort(a + 1, a + 1 + n);
sort(b + 1, b + 1 + m);
for(int i = 1 ; i <= n ; i++) c[i].se = a[i].fi, c[i].fi = a[i].se;
sort(c + 1, c + 1 + n);
int ptr = 0; set<pair<int, int>> s;
for(int i = 1 ; i <= m ; i++)
{
while(ptr < n && c[ptr + 1].fi <= b[i])
{
ptr++;
s.insert({a[ptr].se, ptr});
}
if(s.size() != 0)
{
pair<int, int> x = *s.begin(); s.erase(x);
dp[i] = st.get(1, 1, n, 1, x.se - 1) + 1;
st.update(1, 1, n, i, dp[i]);
}
}
cout << st.get(1, 1, n, 1, n);
}
}
void work()
{
cin >> n >> m;
for(int i = 1 ; i <= n ; i++)
{
cin >> a[i].se >> a[i].fi;
}
for(int i = 1 ; i <= m ; i++) cin >> b[i];
if(n <= 1000 && m <= 1000) return sub1::solve();
sub3::solve();
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
int q = 1;
if(Multitest) cin >> q;
while(q--) work();
}
