#include<bits/stdc++.h>
using namespace std;
const int N = 40010;
int dp[N][2];
int main(){
ios::sync_with_stdio(false); cin.tie(0);
int n, k;
cin >> n >> k;
vector <pair <long long,long long>> v;
for(int i = 1;i <= n;i++){
long long a, b;
cin >> a >> b;
v.push_back({a, b});
}
vector <long long> qr;
for(int i = 1;i <= k;i++){
long long x;
cin >> x;
qr.push_back(x);
}
long long res = 0;
for(int i = 1;i <= n;i++){
dp[k][0] = dp[k][1] = 0;
for(int j = k-1;j >= 0;j--){
dp[j][0] = (min(v[i-1].first, v[i-1].second) <= qr[j] ? dp[j+1][1]+1 : dp[j+1][0]);
dp[j][1] = (max(v[i-1].first, v[i-1].second) <= qr[j] ? dp[j+1][0]+1 : dp[j+1][1]);
}
int a = v[i-1].first, b = v[i-1].second;
if(a == min(a, b)){
if(dp[0][0] % 2 == 0){
res += a;
}
else{
res += b;
}
}
else{
if(dp[0][1]%2 == 0){
res += a;
}
else{
res += b;
}
}
//cout << dp[0][0]<< ' ' << dp[0][1] << '\n';
}
cout << res << '\n';
}
