#include <iostream>
using namespace std;
int N, M;
int card[110][2];
int status[110];
int kk[110];
int main()
{
cin >> N >> M;
for (int x = 0; x < N; x++)
{
cin >> card[x][0] >> card[x][1];
status[x] = 0;
}
for (int x = 0; x < M; x++)
cin >> kk[x];
for (int x = 0; x < M; x++)
{
for (int y = 0; y < N; y++)
{
if (kk[x] > card[y][status[y]])
{
status[y] = 1 - status[y];
}
}
}
int S = 0;
for (int x = 0; x < N; x++)
{
S += card[x][status[x]];
}
cout << S;
}