/*input
3 5
3 1 0 2 0 0 2
*/
#pragma GCC optimize ("O3")
#pragma GCC target("avx,avx2,fma")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
template <typename T>
using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
ll M;
ll L;
cin >> M >> L;
ll A[2 * M + 1];
for (int i = 0; i <= 2 * M; i++)
cin >> A[i];
array<array<pair<ll, ll>, 300>, 301> v;
for (int m = 1; m <= M; m++)
{
for (int k = 0; k < m; k++)
v[m][k] = { -3e18, -3e18};
v[m][0] = {0, 0};
}
ll ret = -1;
for (ll i = 1; i <= M; i++)
{
A[i + M] -= (M + 2) / 2;
if (A[i + M] >= 0)
{
auto w = v;
for (ll m = M / 2 + 1; m <= M; m++)
for (ll k = 0; k < m; k++)
{
ll x = v[m][k].first;
ll mx = (L - x) / i;
mx = min(mx, A[i + M]);
for (ll c = mx; c >= 0 && c >= mx - (M + 2) / 2; c--)
{
ll val = x + i * c;
ll cnt = v[m][k].second + c;
for (ll md = M / 2 + 1; md <= M; md++)
{
ll vv = val % md;
w[md][vv] = max(w[md][vv], {val, cnt});
}
}
}
v = w;
A[i + M] = (M + 2) / 2;
}
else
A[i + M] += (M + 2) / 2;
}
int D = 505500;
vector<int> C(2 * D + 1, -1e9);
C[D] = 0;
int del = 0;
for (int i = 1; i <= M; i++)
{
for (int k = 1; k <= A[i + M]; k++)
{
for (int j = min(D + del, 2 * D - i); j >= max(0, D - del); j--)
{
C[j + i] = max(C[j + i], C[j] + 1);
}
del += i;
}
for (int k = 1; k <= A[-i + M]; k++)
{
for (int j = max(D - del, i); j <= min(D + del, 2 * D); j++)
{
C[j - i] = max(C[j - i], C[j] + 1);
}
if (k > A[i + M])
del += i;
}
}
for (int m = 1; m <= M; m++)
for (int k = 0; k < m; k++)
if (-D <= L - v[m][k].first && L - v[m][k].first <= D)
ret = max(ret, C[D + (L - v[m][k].first)] + v[m][k].second);
if (ret < 0)
cout << "impossible\n";
else
cout << ret + A[M] << "\n";
}
