#include <bits/stdc++.h>
using namespace std;
#define vi vector<int>
#define vll vector<ll>
#define vii vector<pair<int, int>>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define loop(_) for (int __ = 0; __ < (_); ++__)
#define pb push_back
#define f first
#define s second
#define sz(_) ((int)_.size())
#define all(_) _.begin(), _.end()
#define lb lower_bound
#define ub upper_bound
using ll = long long;
using ld = long double;
const int N = 1e5 + 7;
const ll mod = 1e9 + 7;
int n, k;
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
#ifndef ONLINE_JUDGE
#endif
cin >> n >> k;
vii a(n);
for (int i = 0; i < n; ++i)
cin >> a[i].f >> a[i].s;
ll sum = 0;
for (int i = 0; i < n; ++i)
{
sum += a[i].f;
}
while (k--)
{
int x;
cin >> x;
for (int i = 0; i < n; ++i)
{
if (a[i].f <= x)
{
sum -= a[i].f;
swap(a[i].f, a[i].s);
sum += a[i].f;
}
}
}
cout << sum;
return 0;
}
