#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ii pair<int,int>
#define fi first
#define se second
#define endl '\n'
#define puf push_front
#define pof pop_front
#define pub push_back
#define pob pop_back
#define lb lower_bound
#define ub upper_bound
#define rep(x,s,e) for (int x=(s)-((s)>(e));x!=(e)-((s)>(e));((s)<(e))?x++:x--)
#define all(x) (x).begin(),(x).end()
#define sz(x) (int) (x).size()
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int INF=1e18;
int n,k;
int arr[305]; //go pos
int brr[305]; //go neg
int num[305]; //range should be [-neg,pos]
const int LEN=150005;
int memo[2][2*LEN];
int ans;
signed main(){
cin.tie(0);
cout.tie(0);
cin.sync_with_stdio(false);
cin>>n>>k;
rep(x,n+1,1) cin>>arr[x];
cin>>ans;
rep(x,1,n+1) cin>>brr[x];
rep(x,1,n+1) ans+=arr[x]+brr[x];
int curr=0;
rep(x,1,n+1) curr+=(brr[x]-arr[x])*x;
rep(x,n+1,1){
if (curr<k) num[x]=min(arr[x],(k-curr)/x);
else num[x]=-min(brr[x],(curr-k)/x);
curr+=num[x]*x;
ans-=abs(num[x]);
}
rep(x,0,2*LEN) memo[0][x]=-INF;
memo[0][LEN]=0;
int a=0,b=1;
rep(x,1,n+1){
rep(x,0,2*LEN) memo[b][x]=-INF;
deque<ii> dq; //(val,pos)
rep(res,0,x){
dq.clear();
int r=-1;
for (int i=0;res+i*x<2*LEN;i++){
while (res+(r+1)*x<2*LEN && r+1<=i+num[x]){
r++;
ii temp={memo[a][res+r*x]+r+(num[x]<0?-2*num[x]:0),r};
while (!dq.empty() && dq.back().fi<=temp.fi) dq.pob();
dq.pub(temp);
}
while (!dq.empty() && dq.front().se<i+(num[x]-arr[x])) dq.pof();
if (!dq.empty()) memo[b][res+i*x]=dq.front().fi-i;
}
}
dq.clear();
rep(res,0,x){
dq.clear();
int r=-1;
for (int i=0;res+i*x<2*LEN;i++){
while (res+(r+1)*x<2*LEN && r+1<=i+(num[x]+brr[x])){
r++;
ii temp={memo[a][res+r*x]-r+(num[x]>0?2*num[x]:0),r};
while (!dq.empty() && dq.back().fi<=temp.fi) dq.pob();
dq.pub(temp);
}
while (!dq.empty() && dq.front().se<i+(num[x])) dq.pof();
if (!dq.empty())
memo[b][res+i*x]=max(memo[b][res+i*x],dq.front().fi+i);
}
}
swap(a,b);
//rep(x,0,2*LEN){
//if (memo[a][x]<-INF/10) cout<<"-"<<" ";
//else cout<<memo[a][x]<<" ";
//}
//cout<<endl;
}
int pos=k-curr+LEN;
if (0<=pos && pos<2*LEN && memo[a][pos]>-INF/10) cout<<ans+memo[a][pos]<<endl;
else cout<<"impossible"<<endl;
}
