#include <bits/stdc++.h>
#define fo(i, d, c) for (int i = d; i <= c; i++)
#define fod(i, c, d) for (int i = c; i >= d; i--)
#define maxn 1000010
#define fi first
#define se second
#define pb emplace_back
#define en cout << "\n";
#define int long long
#define inf (int)4e18
#define bitcount(x) __builtin_popcountll(x)
#define pii pair<int, int>
#define vii vector<pii>
#define lb(x) x & -x
#define bit(i, j) ((i >> j) & 1)
#define offbit(i, j) (i ^ (1LL << j))
#define onbit(i, j) (i | (1LL << j))
#define vi vector<int>
#define all(x) x.begin(), x.end()
#define ss(x) (int)x.size()
#define UNIQUE(v) v.erase(unique(all(v)),v.end())
template <typename T1, typename T2>
bool minimize(T1 &a, T2 b)
{
if (a > b)
{
a = b;
return true;
}
return false;
}
template <typename T1, typename T2>
bool maximize(T1 &a, T2 b)
{
if (a < b)
{
a = b;
return true;
}
return false;
}
using namespace std;
const int nsqrt = 450;
const int mod = 1e9 + 7;
void add(int &x, int k)
{
x += k;
x %= mod;
if(x < 0) x += mod;
}
void del(int &x, int k)
{
x -= k;
x %= mod;
if(x < 0) x += mod;
}
int m,lim;
int a[maxn],c[maxn];
main()
{
#define name "TASK"
if (fopen(name ".inp", "r"))
{
freopen(name ".inp", "r", stdin);
freopen(name ".out", "w", stdout);
}
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> m >> lim;
fo(i,0,2 * m) cin >> a[i];
int sum = 0;
fo(i,0,m)
{
sum += (i - m) * a[i];
c[i] = a[i];
}
fo(i,m + 1,2 * m)
{
c[i] = min(a[i],(lim - sum) / (i - m));
sum += c[i] * (i - m);
}
fo(i,0,m - 1)
{
int val = min(a[i],(lim - sum) / (m - i));
c[i] -= val;
sum += val * (m - i);
}
if(abs(sum - lim) > m) return cout << "impossible",0;
vii things;
int tot = 0;
fo(i,0,2 * m)
{
tot += c[i];
if(i == m) continue;
int k = 1,s = min(m * m,a[i] - c[i]);
while(k <= s)
{
things.pb(k * (i - m),k);
s -= k;
k *= 2;
}
if(s > 0) things.pb(s * (i - m),s);
k = 1,s = min(c[i],m * m);
while(k <= s)
{
things.pb(k * (m - i),-k);
s -= k;
k *= 2;
}
if(s > 0) things.pb(s * (m - i),-s);
}
int n = ss(things);
int N = m * m;
vi f(2 * N + 10,-inf),dp(2 * N + 10,-inf);
dp[N] = f[N] = 0;
for(auto [val,fre] : things)
{
fo(i,0,2 * N) if(i - val <= 2 * N and i - val >= 0 and dp[i - val] != -inf) maximize(f[i],dp[i - val] + fre);
dp = f;
}
if(f[lim - sum + N] + tot >= 0) cout << f[lim - sum + N] + tot;
else cout << "impossible";
}
