#include <bits/stdc++.h>
#define x first
#define y second
using namespace std;
using ll=long long;
using pii=pair<int,int>;
using vi=vector<int>;
using vl=vector<ll>;
#define pb push_back
#define all(a) begin(a),end(a)

const int N=310,MOD=1e9+7;
const char en='\n';
const ll LLINF=1ll<<60;

int n,w[N],cn[N][N];
pii h[N];
vi cu,pos,prs;
vector<pair<pair<vi,vi>,vi>> pars;

void rek(int s,int mi)
{
	if (s==0)
	{
		pos.pb(cu.size());
		prs.pb(n);
		pars.pb({{cu,pos},prs});
		pos.pop_back();
		prs.pop_back();
		return;
	}
	if (s<mi) return;
	for (int i=max(mi,1);i<=s;++i)
	{
		if (i!=mi) pos.pb(cu.size()),prs.pb(n-s);
		cu.pb(i);
		rek(s-i,i);
		cu.pop_back();
		if (i!=mi) pos.pop_back(),prs.pop_back();
	}
}

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin>>n;
	rek(n,-1);
	for (int i=0;i<n;++i)
	{
		cin>>h[i].x>>h[i].y;
		for (int l=1;l<=n;++l) for (int r=l;r<=n;++r) if (r>=h[i].x && l<=h[i].y) ++cn[l][r];
	}
	for (int i=1;i<=n;++i) cin>>w[i];
	int an=-MOD;
	for (auto x: pars)
	{
		bool ok=1;
		const vi&pos=x.x.y;
		const vi&cu=x.x.x;
		const vi&prs=x.y;
		int posz=pos.size();
		for (int i=0;i<posz;++i) for (int j=i+1;j<posz;++j) if (cn[cu[pos[i]]][cu[pos[j]-1]]<prs[j]-prs[i]) ok=0;
		if (ok)
		{
			int ww=0;
			for (auto y: cu) ww+=w[y];
			an=max(an,ww);
		}
	}
	if (an==-MOD) cout<<"impossible"<<en;
	else cout<<an<<en;
}