/* Author : Mychecksdead */
#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define MOD (1000000000+7)
#define MOD1 (998244353)
#define pb push_back
#define all(x) x.begin(), x.end()
#define en cout << '\n'
const int N = 1e6+100, M = 1e5+10, K = 52, MX = 30;
int n;
pair<int, int> T[N];
ll S[N];
array<ll, 2> a[N];
array<ll, 3> b[N];
void build(int x){
for(int i = 0; i <= 4*x; ++i) T[i] = {x+1, 0};
}
pair<int, int> mx(pair<int, int> x, pair<int, int> y){
swap(x.first, x.second);
swap(y.first, y.second);
if(max(x, y) == x) return {x.second, x.first};
return {y.second, y.first};
}
pair<int, int> get(int l, int r, int ql, int qr, int k){
if(ql > r || l > qr) return {0, 0};
if(ql <= l && r <= qr) return T[k];
int m = l+r>>1;
return mx(get(l, m, ql, qr, k<<1), get(m+1, r, ql, qr, k<<1|1));
}
void update(int l, int r, int p, int k, pair<int, int> val){
if(l == r){
T[k] = mx(val, T[k]);
return;
}
int m = l+r>>1;
if(p <= m) update(l, m ,p, k<<1, val);
else update(m+1, r, p, k<<1|1, val);
T[k] = mx(T[k<<1], T[k<<1|1]);
}
int m;
void solve(){
cin >> n >> m;
for(int i = 1; i <= n; ++i) cin >> a[i][1] >> a[i][0];
for(int i = 1; i <= n; ++i) b[i][0] = a[i][1], b[i][1] = a[i][0], b[i][2] = i;
for(int i = 1; i <= m; ++i) cin >> S[i];
sort(S+1, S+1+m);
sort(a+1, a+1+n);
sort(b+1, b+1+n);
vector<int> val;
// for(int i = 1; i <= n; ++i) val.pb(a[i][1]);
// sort(all(val));
// for(int i = 1; i <= n; ++i) a[b[i][2]][1] = i;
build(m);
for(int i = n; i >= 1; --i){
// cout << a[i][0] << ' ' << a[i][1] << '\n';
int pos = lower_bound(S+1, S+1+m, a[i][1]) - S;
if(pos>m) continue;
pair<int, int> dp = get(1, m, pos, m, 1);
// cout << pos << ' ' << dp.first << ' ' << dp.second << '\n';
if(dp.first >= pos + 1){
// cout << "uwu" << '\n';
update(1, m, dp.first - 1, 1, {dp.first - 1, dp.second + 1});
}
}
int ans = T[1].second;
cout << ans;
}
int main(){
cin.tie(0); ios::sync_with_stdio(0);
int tt = 1, aa;
// freopen("in.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
while(tt--){
solve();
en;
}
cerr<<"time taken : "<<(float)clock()/CLOCKS_PER_SEC<<" seconds\n";
return 0;
}
