#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) begin(a),end(a)
using ar2 = array<int,2>;
using ar3 = array<int,3>;
using ll = long long;
const int mxN = 101;
const int mxSm = 100*100+3;
const int offset = 0;//mxSm+3;
const int INF = (int)1e9;

int n, L, ans;
int l[mxN], r[mxN];
unordered_map<int,int> dp[mxN];//[mxSm+offset];

int32_t main()
{
	ios_base::sync_with_stdio(false); cin.tie(0);
	cin >> n >> L;
	for(int i = n; i >= 1; i--) cin >> l[i];
	int zero; cin >> zero;
	for(int i = 1; i <= n; i++) cin >> r[i];
	for(int i = 0; i <= n; i++)
		for(int j = -mxSm; j <= mxSm; j++)
			dp[i][j+offset] = -INF;
	dp[0][offset]=0;
	for(int i = 1; i <= n; i++){
		for(int j = -mxSm; j <= mxSm; j++){
			for(int k = -l[i]; k <= r[i]; k++){
				int val = abs(k);
				if(k<0) val+=min(abs(k-l[i]),r[i]);
				else if(k>0) val+=min(abs(l[i]),abs(r[i]-k));
				else val+=min(abs(l[i]),abs(r[i]));
				int old_j = j-k*i;
				if(abs(old_j)<=mxSm){
					j+=offset;
					dp[i][j] = max(dp[i][j], dp[i-1][old_j+offset]+val);
					j-=offset;
				}
			}
			if(i==n and j==L) ans=dp[i][j];
		}
	}
	if(ans<0){cout<<"impossible";return 0;}
	cout << ans+zero << "\n";
}