#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#define fi first
#define se second
using namespace std;
typedef pair<int, int> pii;
typedef long long ll;
int M, K;
ll L, S, arr[1010], rem[1010], ans;
int dp[2][202020];
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> M >> L; K = 2*M*M;
for (int i = 0; i <= 2*M; i++) cin >> arr[i];
for (int i = 0; i <= 2*M; i++) S += (i-M)*arr[i];
if (S < L) {
L = -L;
for (int i = 0; i <= M; i++) swap(arr[i], arr[2*M-i]);
}
S = 0;
for (int i = 0; i <= M; i++) {
S += (i-M)*arr[i];
ans += arr[i];
rem[2*M-i] = arr[i];
arr[i] = 0;
}
if (S > L) {
cout << "impossible\n";
return 0;
}
for (int i = M+1; i <= 2*M; i++) {
ll t = (L-S)/(i-M);
if (t >= arr[i]) {
ans += arr[i];
rem[2*M-i] = arr[i];
S += arr[i]*(i-M);
arr[i] = 0;
}
else {
ans += t;
rem[2*M-i] = t;
S += t*(i-M);
arr[i] -= t;
break;
}
}
for (int j = 0; j <= K; j++) dp[0][j] = -1e9;
dp[0][M*M] = 0;
for (int i = 1; i <= M; i++) {
for (int r = 0; r < i; r++) {
deque< pair<int, int> > dq1, dq2;
for (int j = r; j <= K; j += i) {
while (dq1.size() > 0 && (j-dq1.front().fi)/i > arr[M+i]) dq1.pop_front();
while (dq1.size() > 0 && dq1.back().se + (j-dq1.back().fi)/i <= dp[0][j]) dq1.pop_back();
dq1.push_back({j, dp[0][j]});
while (dq2.size() > 0 && (j-dq2.front().fi)/i > rem[M+i]) dq2.pop_front();
while (dq2.size() > 0 && dq2.back().se - (j-dq2.back().fi)/i <= dp[0][j]) dq2.pop_back();
dq2.push_back({j, dp[0][j]});
dp[1][j] = max(dq1.front().se + (j-dq1.front().fi)/i,
dq2.front().se - (j-dq2.front().fi)/i);
}
}
memcpy(dp[0], dp[1], sizeof(int)*(K+1));
//for (int j = 0; j <= K; j++) dp[0][j] = dp[1][j];
}
for (int i = 1; i <= M; i++) {
for (int r = 0; r < i; r++) {
deque< pair<int, int> > dq1, dq2;
int j = r;
while (j+i <= K) j += i;
for (; j >= r; j -= i) {
while (dq1.size() > 0 && (dq1.front().fi-j)/i > arr[M-i]) dq1.pop_front();
while (dq1.size() > 0 && dq1.back().se + (dq1.back().fi-j)/i <= dp[0][j]) dq1.pop_back();
dq1.push_back({j, dp[0][j]});
while (dq2.size() > 0 && (dq2.front().fi-j)/i > rem[M-i]) dq2.pop_front();
while (dq2.size() > 0 && dq2.back().se - (dq2.back().fi-j)/i <= dp[0][j]) dq2.pop_back();
dq2.push_back({j, dp[0][j]});
dp[1][j] = max(dq1.front().se + (dq1.front().fi-j)/i,
dq2.front().se - (dq2.front().fi-j)/i);
}
}
memcpy(dp[0], dp[1], sizeof(int)*(K+1));
//for (int j = 0; j <= K; j++) dp[0][j] = dp[1][j];
}
if (dp[0][L-S+M*M] <= -1e8) cout << "impossible\n";
else cout << ans + dp[0][L-S+M*M] << "\n";
return 0;
}
