#include <bits/stdc++.h>
using namespace std;
const int N = int(6e5) + 9;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int m;
cin >> m;
long long L;
cin >> L;
vector<int> a(2 * m + 1);
for (int i = -m; i <= m; i++) {
cin >> a[i + m];
}
vector<int> dp(2 * N + 1, -1), ndp(2 * N + 1, -1);
dp[N] = 0;
for (int i = -m; i <= m; i++) {
for (int x = -N; x <= N; x++) {
ndp[x + N] = -1;
}
for (int x = -N; x <= N; x++) {
if (dp[x + N] == -1) continue;
for (int j = 0; j <= a[i + m]; j++) {
int k = x + i * j;
if (-N <= k && k <= N) {
k += N;
ndp[k] = max(ndp[k], dp[x + N] + j);
}
}
}
swap(dp, ndp);
}
L += N;
if (0 <= L && L <= 2 * N) {
if (dp[L] == -1) {
cout << "impossible" << '\n';
} else {
cout << dp[L] << '\n';
}
} else {
cout << "impossible" << '\n';
}
return 0;
}
