#include <bits/stdc++.h>
#define iter(a) a.begin(), a.end()
#define lsort(a) sort(iter(a))
#define gsort(a) sort(iter(a), greater<>())
#define eb emplace_back
#define pob pop_back()
#define ef emplace_front
#define pof pop_front()
#define mp make_pair
#define F first
#define S second
#define uni(a) a.resize(unique(iter(a)) - a.begin())
#define printv(a, b) { \
for(auto pv : a) b << setw(4) << pv << " "; \
b << "\n"; \
}
using namespace std;
typedef long long ll;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const ll MAX = 1LL << 60;
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
int M, L;
cin >> M >> L;
assert(M <= 100);
vector<ll> cnt(2 * M + 1);
ll mx = 0, mn = 0;
for(int i = 0; i <= 2 * M; i++){
cin >> cnt[i];
assert(cnt[i] <= 100);
if(i - M > 0) mx += (i - M) * cnt[i];
if(i - M < 0) mn += (i - M) * cnt[i];
}
//cerr << "ok\n";
if(L < mn || mx < L){
cout << "impossible\n";
return 0;
}
ll total = mx - mn + 1;
vector<ll> dp(total + 1, -1);
dp[-mn] = cnt[M];
//cerr << "test " << 0 << " ";
//printv(dp, cerr);
for(int i = 0; i < M; i++){
int t = -(i - M);
auto calc = [&](int x){
return dp[x] + x / t;
};
vector<deque<pll>> dq(t);
for(int j = total - 1; j >= 0; j--){
int id = j % t;
while(!dq[id].empty() && dq[id].front().F / t > j / t + cnt[i]) dq[id].pof;
while(!dq[id].empty() && dq[id].back().S <= calc(j)) dq[id].pob;
if(dp[j] != -1){
//cerr << "push " << j << " " << calc(j) << "\n";
dq[id].eb(mp(j, calc(j)));
}
if(dq[id].empty()) continue;
dp[j] = dq[id].front().S - j / t;
}
//cerr << "test " << -t << " ";
//printv(dp, cerr);
}
vector<ll> dp2(total, -MAX);
for(int i = M + 1; i <= 2 * M; i++){
int t = i - M;
auto calc = [&](int x){
return dp[x] - x / t;
};
vector<deque<pii>> dq(t);
for(int j = 0; j < total; j++){
int id = j % t;
while(!dq[id].empty() && dq[id].front().F / t < j / t - cnt[i]) dq[id].pof;
while(!dq[id].empty() && dq[id].back().S <= calc(j)) dq[id].pob;
if(dp[j] != -1){
//cerr << "push " << j << " " << calc(j) << "\n";
dq[id].eb(mp(j, calc(j)));
}
if(dq[id].empty()) continue;
dp[j] = dq[id].front().S + j / t;
}
//cerr << "test " << t << " ";
//printv(dp, cerr);
}
if(dp[-mn + L] < 0) cout << "impossible\n";
else cout << dp[-mn + L] << "\n";
return 0;
}
