#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int MAXN = 1010;
int n, k;
int cards[MAXN][2];
int which[MAXN];
int main() {
ios::sync_with_stdio(0), cin.tie(0);
cin >> n >> k;
for (int i = 0; i < n; i++) {
cin >> cards[i][0] >> cards[i][1];
}
for (int i = 0; i < n; i++) which[i] = 0;
for (int _ = 0; _ < k; _++) {
int t;
cin >> t;
for (int i = 0; i < n; i++) {
if (cards[i][which[i]] <= t) {
which[i] = 1 - which[i];
}
}
}
ll tot = 0;
for (int i = 0; i < n; i++) {
tot += cards[i][which[i]];
}
cout << tot << '\n';
return 0;
}
