#include <bits/stdc++.h>
#define int ll
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define rng(i,c,n) for(int i=c;i<n;i++)
#define fi first
#define se second
#define pb push_back
#define sz(a) (int) a.size()
#define all(a) a.begin(),a.end()
#define vec(...) vector<__VA_ARGS__>
#define _3M8yqhy ios::sync_with_stdio(0),cin.tie(0)
typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pii;
void print(){cout<<'\n';}
template<class h,class...t>
void print(const h&v,const t&...u){cout<<v<<' ',print(u...);}

#define nare cout<<"impossible\n"; return;

const int inf=1e18;

void chmax(int&a,int b){
	a=max(a,b);
}

void slv(){
	int n;
	cin>>n;

	vec(pii) a(n);
	rep(i,n){
		cin>>a[i].fi>>a[i].se;
	}

	vi wit(n+1);
	rng(i,1,n+1){
		cin>>wit[i];
	}

	vi open(n+1),close(n+1);
	rep(i,n){
		open[a[i].fi]+=1;
		close[a[i].se]+=1;
	}

	// dp[point][overall chosen][open and chosen] = { maximum value }
	vec(vi) dp(n+1,vi(n+1,-inf)),ndp1,ndp;
	dp[0][0]=0;
	int now=0;
	rng(i,1,n+1){
		ndp=vec(vi)(n+1,vi(n+1,-inf));
		int ad=open[i];
		now+=ad;
		rep(j,n+1){
			rep(k,n+1){
				if(dp[j][k]==-inf) continue;
				rep(take,2){
					if(now>=k+take*i){
						int nj=j+take*i;
						int nk=k+take*i;
						chmax(ndp[nj][nk],dp[j][k]+take*wit[i]);
					}
				}
			}
		}
		ndp1=vec(vi)(n+1,vi(n+1,-inf));
		now-=close[i];
		rep(j,n+1){
			rep(k,n+1){
				int nk=k-close[i];
				if(nk<0 or nk>now) continue;
				ndp1[j][nk]=ndp[j][k];
				// chmax(ndp1[j][nk],ndp[j][k]);
			}
		}
		dp.swap(ndp1);
	}
	if(dp[n][0]==-inf){
		nare;
	}
	cout<<dp[n][0]<<"\n";
}

signed main(){
_3M8yqhy;
	slv();
}