#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define MASK(x) (1LL << (x))
#define BIT(x, i) (((x) >> (i)) & 1)
#define SZ(x) ((int) (x).size())
#define ALL(a) (a).begin(), (a).end()
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define FORD(i, a, b) for (int i = (a), _b = (b); i >= _b; --i)
#define REP(i, n) for (int i = 0, _n = (n); i < _n; ++i)
#define debug(x) cout << "[" << #x << " = " << (x) << "]" << endl
#define left __left
#define right __right
#define prev __prev
#define next __next
#define fi first
#define se second
template <class X, class Y>
bool maximize(X &x, Y y) {
if (x < y) return x = y, true;
else return false;
}
template <class X, class Y>
bool minimize(X &x, Y y) {
if (x > y) return x = y, true;
else return false;
}
const int inf = (int) 1e9 + 7;
#define MAX_N 100'100
int numPic, numFrame;
int frame[MAX_N + 2];
struct Pic {
int sz, val;
void input() {
cin >> sz >> val;
}
bool operator < (const Pic &other) const {
if (val != other.val) return val < other.val;
return sz < other.sz;
}
} pic[MAX_N + 2];
namespace subtask2 {
bool check() {
return (max(numPic, numFrame) <= 1000);
}
int dp[1010][1010];
void solve() {
int ans = 0;
FOR(i, 1, numPic) FOR(j, 1, numFrame) {
dp[i][j] = dp[i - 1][j];
if (pic[i].sz <= frame[j]) maximize(dp[i][j], dp[i - 1][j - 1] + 1);
maximize(ans, dp[i][j]);
}
cout << ans;
}
}
int main() {
ios_base::sync_with_stdio(false);cin.tie(nullptr);
#define task "test"
if (fopen(task".inp","r")) {
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
cin >> numPic >> numFrame;
/// frame & val inc , not sz & val inc; huhu;
FOR(i, 1, numPic) pic[i].input();
FOR(i, 1, numFrame) cin >> frame[i];
sort(pic + 1, pic + 1 + numPic);
sort(frame + 1, frame + 1 + numFrame);
if (subtask2 :: check()) return subtask2 :: solve(), 0;
return 0;
}
/* Discipline - Calm */
