//reading is hard
#include <bits/stdc++.h>
using namespace std;
template<class T, class U>
void ckmin(T &a, U b)
{
if (a > b) a = b;
}
template<class T, class U>
void ckmax(T &a, U b)
{
if (a < b) a = b;
}
#define MP make_pair
#define PB push_back
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define FOR(i, a, b) for (auto i = (a); i < (b); i++)
#define FORD(i, a, b) for (auto i = (a) - 1; i >= (b); i--)
#define SZ(x) ((int) ((x).size()))
#define ALL(x) (x).begin(), (x).end()
#define INF 1000000007
#define LLINF 2696969696969696969ll
#define MAXN 100013
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pii> vpi;
typedef vector<pll> vpl;
int N, M;
pii arr[MAXN];
int lim[MAXN];
vi dp;
bool check(int x)
{
//you need smth 0...x - 1
vi nums;
FOR(i, 0, x)
{
nums.PB(lim[M - 1 - i]);
}
reverse(ALL(nums));
// for (int x : nums)
// {
// cerr << x << ' ';
// }
// cerr << endl;
int iter = 0;
FOR(i, 0, x)
{
while(iter < N && arr[iter].se > nums[i]) iter++;
iter++;
}
return (iter <= N);
}
int32_t main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> N >> M;
FOR(i, 0, N)
{
cin >> arr[i].se >> arr[i].fi;
}
sort(arr, arr + N);
FOR(i, 0, M)
{
cin >> lim[i];
}
sort(lim, lim + M);
int lo = 0, hi = min(N, M);
while(hi > lo)
{
int mid = (hi + lo + 1) >> 1;
if (check(mid)) lo = mid;
else hi = mid - 1;
}
cout << lo << '\n';
}
