#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> ii;
typedef vector<ll> vll;
typedef pair<long long, long long> pll;
typedef pair<char, ll> ci;
typedef pair<string, ll> si;
typedef long double ld;
typedef vector<ll> vi;
typedef vector<string> vs;
#define pb push_back
#define fi first
#define se second
#define whole(v) v.begin(), v.end()
#define rwhole(v) v.rbegin(), v.rend()
#define inf INT_MAX/2
#define fro front
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
ll n, k; cin >> n >> k;
vector<ii> x(n);
for(ll i = 0; i < n; ++i){
cin >> x[i].fi >> x[i].se;
}
vector<ll> que;
for(ll i = 0; i < k; ++i){
ll a; cin >> a;
que.pb(a);
}
for(auto e:que){
for(ll i = 0; i < n; ++i){
if(x[i].fi <= e){
swap(x[i].fi, x[i].se);
}
}
}
ll cnt = 0;
for(auto e:x){
cnt += e.fi;
}
cout << cnt << endl;
}
