#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse4")
#define endl '\n'
using namespace std;
const int maxn = 2e5 + 3;
int n, k;
int a[maxn], b[maxn], 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];
}
void solve()
{
long long ans = 0;
for (int i = 1; i <= n; i++)
{
bool is = false;
for (int j = 1; j <= k; j++)
{
int border = (is ? b[i] : a[i]);
if (t[j] >= border)
is ^= 1;
}
if (!is)
ans += a[i];
else
ans += b[i];
}
cout << ans << endl;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
read();
solve();
}
