#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define ll long long
#define pi pair<int, int>
#define vi vector<int>
#define fi first
#define se second
#define mod 998244353
template<typename T> bool chkmin(T &a, T b){return (b < a) ? a = b, 1 : 0;}
template<typename T> bool chkmax(T &a, T b){return (b > a) ? a = b, 1 : 0;}
#define N 310
#define M (N * N * 2)
int m, val[N * 2], s[M];
ll l, a[N * 2], b[N * 2];
pi dq[M];
void uup(int *s, int w, ll cnt, int d) {
for (int i = 0; i < w; ++i) {
int fr = 0, ba = 0;
for (int j = i, k = 0; j < M; j += w, ++k) {
int cur = s[j] - k * d;
while (fr < ba && dq[ba - 1].fi <= cur) --ba;
dq[ba++] = mp(cur, j);
s[j] = k * d + dq[fr].fi;
if (dq[fr].se + cnt * w == j) ++fr;
}
}
}
void udown(int *s, int w, ll cnt, int d) {
for (int i = 0; i < w; ++i) {
int fr = 0, ba = 0, k = M / w;
if (w * k + i >= M) --k;
for (int j = k * w + i; k >= 0; --k, j -= w) {
int cur = s[j] + k * d;
while (fr < ba && dq[ba - 1].fi <= cur) --ba;
dq[ba++] = mp(cur, j);
s[j] = dq[fr].fi - k * d;
if (dq[fr].se - cnt * w == j) ++fr;
}
}
}
void solve() {
scanf("%d%lld", &m, &l);
ll sum = 0;
for (int i = 0; i < m; ++i) {
scanf("%lld", &a[m - i - 1]);
val[m - i - 1] = m - i;
l += a[m - i - 1] * (m - i);
sum += a[m - i - 1];
}
for (int i = 0; i <= m; ++i) {
scanf("%lld", &a[2 * m - i]);
val[2 * m - i] = i;
}
sum += a[2 * m];
for (int i = 2 * m - 1; i >= 0; --i) {
ll take = min(l / val[i], a[i]);
l -= take * val[i];
sum += take * (i >= m ? 1 : -1);
a[i] -= take;
b[i] += take;
if (a[i]) break;
}
memset(s, 0xc3, sizeof s);
s[M / 2] = 0;
for (int i = 0; i < 2 * m; ++i) {
if (a[i]) uup(s, val[i], a[i], i < m ? -1 : 1);
if (b[i]) udown(s, val[i], b[i], i < m ? 1 : -1);
}
if (l < 0 || l + M / 2 >= M || s[l + M / 2] < -M) printf("impossible\n");
else printf("%lld\n", s[l + M / 2] + sum);
}
int main() {
int T = 1;
//scanf("%d", &T);
while (T--) solve();
return 0;
}
