#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#define endl '\n'
using namespace std;
const int maxn = 2e5 + 3;
int n, k;
int a[maxn], b[maxn];
int t[maxn];
void read()
{
cin >> n >> k;
for (int i = 1; i <= n; i++)
cin >> a[i] >> b[i];
for (int i = 1; i <= k; i++)
cin >> t[i];
}
int tr[maxn * 4];
void merge(int v)
{
tr[v] = max(tr[v * 2], tr[v * 2 + 1]);
}
void build(int v, int l, int r)
{
if (l == r)
{
tr[v] = t[l];
return;
}
int mid = (l + r) / 2;
build(v * 2, l, mid);
build(v * 2 + 1, mid + 1, r);
merge(v);
}
int first, second;
void f(int v, int l, int r)
{
if (tr[v] < first)
return;
if (l == r)
{
swap(first, second);
return;
}
int mid = (l + r) / 2;
f(v * 2, l, mid);
f(v * 2 + 1, mid + 1, r);
}
void solve()
{
build(1, 1, k);
long long ans = 0;
for (int i = 1; i <= n; i++)
{
first = a[i], second = b[i];
f(1, 1, k);
ans += first;
}
cout << ans << endl;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
read();
solve();
}
