#include <bits/stdc++.h>
#define int long long
#define fi first
#define sc second
using namespace std;
const int N = 2e5 + 5, INF = 2e9;
int n, k, ans, x[N];
pair<int, int> a[N];
set<int> s;
unordered_map<int, int> v;
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> k;
for(int i = 1;i<=n;i++) cin >> a[i].fi >> a[i].sc;
for(int i = 1;i<=k;i++) cin >> x[i], s.insert(x[i]);
sort(a + 1, a + n + 1);
for(int i = 1;i<=n;i++){
auto it = s.lower_bound(a[i].fi);
int l = -INF, r = INF;
if(it != s.end()) r = *it;
if(it != s.begin()){
--it;
l = *it;
}
if(min(r - a[i].fi, a[i].fi - l) >= a[i].sc) ans += a[i].sc;
else{
ans += min(r - a[i].fi, a[i].fi - l);
if(r - a[i].fi == a[i].fi - l){
if(!v[l] && !v[r]){
v[r] = 1;
++ans;
}
}else if(a[i].fi - l < r - a[i].fi){
if(!v[l]) v[l] = 1, ++ans;
}else{
if(!v[r]) v[r] = 1, ++ans;
}
}
}
cout << ans;
}
