#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; i++)
#define FORD(i, b, a) for (int i = (b), _a = (a); i >= _a; i--)
#define pa pair<ll, ll>
#define fi first
#define se second
#define bit(mask, j) ((mask >> j) & 1)
#define t_test int t;cin >> t;while(t--)
const ll mod = 1e9 + 7;
const ll INF = 1e17;
inline void adm(ll &x){if(x>=mod)x%=mod;else if(x<0)x+=mod;}
//--------------------------------------------------------------------
const ll N = 1e5 + 10;
struct Node {
ll val, id;
} st[N];
ll n, m;
pa a[N];
ll c[N];
void update(ll x, ll val, ll id = 1, ll l = 1, ll r = n) {
if(x < l || x > r) return;
if(l == r) {
st[id].val = val;
st[id].id = l;
return;
}
ll mid = l + r >> 1;
update(x, val, id << 1, l, mid);
update(x, val, id << 1 | 1, mid + 1, r);
if(st[id << 1].val > st[id << 1 | 1].val) {
st[id] = st[id << 1];
}
else st[id] = st[id << 1 | 1];
}
Node get(ll u, ll v, ll id = 1, ll l = 1, ll r = n) {
if(u > r || v < l) {
return {-INF, - 1};
}
if(u <= l && v >= r) {
return st[id];
}
ll mid = l + r >> 1;
Node x = get(u, v, id << 1 , l, mid);
Node y = get(u, v, id << 1 | 1, mid + 1, r);
if(x.val > y.val) {
return x;
}
return y;
}
void hbmt() {
cin >> n >> m;
FOR(i, 1, n) cin >> a[i].fi >> a[i].se;
sort(a + 1, a + n + 1);
FOR(i, 1, m) {
cin >> c[i];
}
FOR(i, 1, n) {
update(i, a[i].se);
}
sort(c + 1,c + m + 1);
ll mx = INF;
ll cnt = 0;
while(n > 0 && m > 0) {
if(a[n].fi > c[m]) {
n--;
continue;
}
while(true) {
Node x = get(1, n);
if(x.val == -INF) {
cout << cnt;
return;
}
update(x.id,-INF);
if(x.val <= mx) {
mx = x.val;
cnt++;
break;
}
}
n--, m--;
}
cout << cnt;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
if(fopen("hbmt.inp", "r")) {
freopen("hbmt.inp", "r", stdin);
freopen("hbmt.out", "w", stdout);
}
// t_test
hbmt();
return 0;
}
