#include <bits/stdc++.h>
using namespace std;
template<typename T>
void out(T x) { cout << x << endl; exit(0); }
#define watch(x) cout << (#x) << " is " << (x) << endl
using ll = long long;
const ll mod = 1e9+7;
const int maxn = 1e6 + 5;
int n, k;
ll card[maxn][2];
bool state[maxn];
void proc(int x) {
for (int i=1; i<=n; i++) {
if (card[i][state[i]]<=x) {
state[i]=!state[i];
}
}
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>>n>>k;
for (int i=1; i<=n; i++) {
cin>>card[i][0]>>card[i][1];
}
while (k--) {
int x;
cin>>x;
proc(x);
}
ll sum = 0;
for (int i=1; i<=n; i++) {
sum += card[i][state[i]];
}
cout<<sum<<endl;
return 0;
}
