#include <bits/stdc++.h>
using namespace std;
#define int long long
const int INF = 1e18;
const int MOD = 1e9+7;
const int MAXN = 2e5;
int n, m;
int arr[5][MAXN+5];
bool stat[MAXN+5];
void solve(){
cin >> n >> m;
for(int i = 1; i <= n; i++) cin >> arr[0][i] >> arr[1][i];
while(m--){
int t; cin >> t;
for(int i = 1; i <= n; i++){
if(arr[stat[i]][i] <= t) stat[i] ^= 1;
}
}
int ans = 0;
for(int i = 1; i <= n; i++) ans += arr[stat[i]][i];
cout << ans << endl;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int tc = 1;
// cin >> tc;
while(tc--){
solve();
}
return 0;
}
/*
5 3
4 6
9 1
8 8
4 2
3 7
8
2
9
=> 18
*/
