#include<algorithm>
#include<complex>
#include<iostream>
#include<map>
#include<queue>
#include<set>
#include<stdint.h>
#include<vector>
#ifdef LOCAL
#include "dbg.h"
#else
#define dbg(...)
#endif
using namespace std;
const int64_t INF = (int64_t) 1e18 + 777;
const int64_t mINF = (int64_t) 1e9 + 777;
const int64_t MOD = (int64_t) 1e9 + 7;
struct Picture
{
int s; int v;
Picture(int s_, int v_) : s(s_), v(v_) {}
bool operator < (const Picture& o)
{
return v < o.v;
}
};
struct Solution
{
vector<int> bit;
Solution() {}
void solve()
{
int n; int m;
cin >> n >> m;
vector<Picture> pic;
vector<int> c(m);
for(int i = 0; i < n; i++)
{
int s; int v;
cin >> s >> v;
pic.emplace_back(s, v);
}
for(int i = 0; i < m; i++)
{
cin >> c[i];
}
bit.resize(m + 1, 0);
vector<bool> taken(m, false);
sort(c.begin(), c.end());
sort(pic.begin(), pic.end());
int ans = 0;
for(int i = 0; i < n; i++)
{
int s = pic[i].s;
int l = 0; int r = m - 1;
int x = -1;
while(l <= r)
{
int mid = l + (r - l) / 2;
if(c[mid] >= s)
{
x = mid;
if(taken[mid]) l = mid + 1;
else r = mid - 1;
}
else l = mid + 1;
}
if(x == -1) continue;
taken[x] = true;
int dp = get(x);
ans = max(ans, dp + 1);
update(x + 1, dp + 1);
}
cout << ans << "\n";
}
int get(int i)
{
int res = 0;
while(i > 0)
{
res = max(res, bit[i]);
i -= i & (-i);
}
return res;
}
void update(int i, int val)
{
while(i < (int) bit.size())
{
bit[i] = max(bit[i], val);
i += i & (-i);
}
}
int modadd(int a, int b)
{
int res = a + b;
if(res >= MOD) res -= MOD;
return res;
}
int modmul(int a, int b)
{
return (1LL * a * b) % MOD;
}
};
int main()
{
int t = 1;
//cin >> t;
for(int i = 0; i < t; i++)
{
Solution().solve();
}
return 0;
}
