#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define endl '\n'
using namespace std;
const int maxn = 2e5 + 3;
int n, k;
int a[maxn][2], t[maxn];
void read()
{
cin >> n >> k;
for (int i = 1; i <= n; i++)
cin >> a[i][0] >> a[i][1];
for (int i = 1; i <= k; i++)
cin >> t[i];
}
void solve()
{
long long ans = 0;
for (int i = 1; i <= n; i++)
{
bool is = false;
for (int j = 1; j <= k; j++)
if (t[j] >= a[i][is])
is ^= 1;
ans += a[i][is];
}
cout << ans << endl;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
read();
solve();
}
