#include <bits/stdc++.h>
using namespace std;
#ifdef DEBUG
#define dbg(...) printf(__VA_ARGS__);
#define getchar_unlocked getchar
#else
#define dbg(...)
#endif
#define sf scanf
#define pf printf
#define fi first
#define se second
#define pb push_back
#define psf push_front
#define ppb pop_back
#define ppf pop_front
#define sz(x) (int)x.size()
#define mnto(x,y) x=min(x,(__typeof__(x))y)
#define mxto(x,y) x=max(x,(__typeof__(x))y)
#define INF 1023456789
#define LINF 1023456789123456789
#define all(x) x.begin(),x.end()
#define lb(x,v) (lower_bound(all(x),v)-x.begin())
#define ub(x,v) (upper_bound(all(x),v)-x.begin())
#define disc(x) sort(all(x));x.resize(unique(all(x))-x.begin());
typedef long long ll;
typedef long double ld;
typedef pair<int,int> ii;
typedef pair<ll,ll> pll;
typedef tuple<int,int,int> iii;
typedef tuple<int,int,int,int> iiii;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<ii> vii;
mt19937 rng(time(0));
#define mod 1000000007
inline int add(int a,int b){
int r=a+b; while(r>=mod)r-=mod;
while(r<0)r+=mod;
return r;
}
inline int mult(int a,int b){
return (int)(((ll)(a*b))%mod);
}
inline int rd(){
int x=0;
char ch=getchar_unlocked();
while(!(ch&16))ch=getchar();//keep reading while current character is whitespace
while(ch&16){//this will break when ‘\n’ or ‘ ‘ is encountered
x=(x<<3)+(x<<1)+(ch&15);
ch=getchar_unlocked();
}
return x;
}
#define maxn 1005
#define maxv 200005
int n,m,v,up[maxn],num[maxn];
ll l,a[maxn],take[maxn],dp[maxv];
void update(int num,int val,int cost){
int cnt=0;
while(num){
int iter=1;
if(num%2==0)iter=2;
num=(num-1)/2;
for(int i=0;i<iter;++i){
if(val>=0){
for(int i=v;i>=-v;--i){
int cur=val*(1<<cnt);
if(i+cur<=v)mxto(dp[i+cur+v],dp[i+v]+cost*(1<<cnt));
}
}
else{
for(int i=-v;i<=v;++i){
int cur=val*(1<<cnt);
if(-v<=i+cur)mxto(dp[i+cur+v],dp[i+v]+cost*(1<<cnt));
}
}
}
++cnt;
}
}
int main(){
sf("%d%lld",&m,&l);
ll tot=0,pos=0;
n=2*m+1;v=m*m;
for(int i=0;i<n;++i){
up[i]=i-m;
sf("%lld",&a[i]);
tot+=a[i]*up[i];
if(up[i]>0)pos+=a[i]*up[i];
}
if(pos<l){
pf("impossible\n");
exit(0);
}
ll cur=0,ans=0;
if(tot>=l){
for(int i=0;i<n;++i){
if(up[i]<=0)take[i]=a[i];
else take[i]=min(a[i],(l-cur)/up[i]);
cur+=take[i]*up[i];
ans+=take[i];
}
}
else{
for(int i=n-1;i>=0;--i){
if(up[i]>=0)take[i]=a[i];
else take[i]=min(a[i],(cur-l)/(-up[i]));
cur+=take[i]*up[i];
ans+=take[i];
}
}
assert(l-m<=cur&&cur<=l+m);
for(int i=-v;i<=v;++i)dp[i+v]=-LINF;
dp[cur-l+v]=ans;
for(int i=0;i<n;++i){
update((int)min((ll)2*m,a[i]-take[i]),up[i],1);
update((int)min((ll)2*m,take[i]),-up[i],-1);
}
if(dp[v]<0)pf("impossible\n");
else pf("%lld\n",dp[v]);
}
/*
2 5
2 3 1 1 4
3 5
3 1 0 2 0 0 2
1 5
0 0 6
*/
