#include <bits/stdc++.h>
//#pragma GCC optimize("O3")
//#pragma GCC optimize("unroll-loops")
#include <ext/pb_ds/assoc_container.hpp> //required
#include <ext/pb_ds/tree_policy.hpp> //required
using namespace __gnu_pbds; //required
using namespace std;
template <typename T> using indexed_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define int long long
#define vi vector<int>
#define vl vector<long long>
#define vii vector<pair<int,int>>
#define vll vector<pair<long long,long long>>
#define pb push_back
#define ll long long
#define ld long double
#define nl '\n'
#define boost ios::sync_with_stdio(false)
#define mp make_pair
#define se second
#define fi first
#define fore(i, y) for(int i = 0; i < y; i++)
#define forr(i,x,y) for(int i = x;i<=y;i++)
#define forn(i,y,x) for(int i = y; i >= x; i--)
#define all(v) v.begin(),v.end()
#define sz(v) v.size()
#define clr(v,k) memset(v,k,sizeof(v))
#define rall(v) v.rbegin() , v.rend()
#define pii pair<int,int>
#define pll pair<ll , ll>
const ll MOD = 1e9 + 7;
const ll INF = 1e18 + 1;
ll gcd(ll a , ll b) {return b ? gcd(b , a % b) : a ;} // greatest common divisor (gcd)
ll lcm(ll a , ll b) {return a * (b / gcd(a , b));} // least common multiple (lcm)
// HERE IS THE SOLUTION
vl st;
void build(vi &a , int &n)
{
while(__builtin_popcount(n) != 1)
{
n++;
a.pb(-INF);
}
st.resize(2*n);
fore(i , n)
{
st[i + n] = a[i];
}
forn(i ,n - 1, 1)
{
st[i] = max(st[2*i] , st[2*i + 1]);
}
}
void update(int i , int v , int n)
{
st[i + n] = v;
for(int j = (n + i)/2;j>= 1;j/=2)
{
st[j] = max(st[2*j] , st[2*j + 1]);
}
}
int query(int node , int nodeL , int nodeR , int queryL , int queryR)
{
if(nodeL >= queryL && nodeR<= queryR)
{
return st[node];
}
if(nodeL > queryR || nodeR < queryL)
{
return -INF;
}
int mid = (nodeL + nodeR)/2;
return max(query(2*node , nodeL , mid , queryL , queryR) , query(2*node + 1 , mid + 1 , nodeR , queryL , queryR));
}
signed main()
{
cin.tie(0);
cout.tie(0);
boost;
int n , m;
cin>>n>>m;
vi s(n) , v(n);
vii A(n);
fore(i , n)
{
cin>>s[i]>>v[i];
A[i] = {s[i] , v[i]};
}
sort(all(A));
map<int ,set<int>> ls;
fore(i , n)
{
v[i] = A[i].se;
ls[v[i]].insert(i);
s[i] = A[i].fi;
}
build(v , n);
vi frame(m);
fore(i , m)
{
cin>>frame[i];
}
sort(rall(frame));
int ans = 0;
forr(i , 0 , m - 1)
{
int idx = upper_bound(all(s) , frame[i]) - s.begin();
idx--;
if(idx < 0)
{
break;
}
int mx = query(1 , 0 , n -1 , 0 , idx);
if(mx == -INF)
{
break;
}
auto lst = ls[mx].upper_bound(idx);
lst--;
update(*lst , -INF , n);
ls[mx].erase(lst);
ans++;
}
cout<<ans<<nl;
}
