// author: erray
#undef DEBUG
#include <bits/stdc++.h>
#ifdef DEBUG
#include "debug.h"
#else
#define debug(...) void(37)
#endif
using namespace std;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
int M;
long long L;
cin >> M >> L;
vector<long long> neg(M), pos(M);
long long banked = 0;
for (int i = 0; i < M; ++i) {
cin >> neg[M - i - 1];
}
cin >> banked;
for (int i = 0; i < M; ++i) {
cin >> pos[i];
}
if (L < 0) {
swap(neg, pos);
L = -L;
}
const int inf = int(1e9);
vector<int> dp(M * M + 1, -inf);
dp[0] = 0;
auto Push = [&](int x, long long c, int delta) {
bool rev = false;
if (x < 0) {
rev = true;
x = -x;
reverse(dp.begin(), dp.end());
}
for (int r = 0; r < x; ++r) {
deque<pair<int, int>> dq;
for (int i = r, ps = 0; i < int(dp.size()); i += x, ++ps) {
int push = dp[i] + (ps * -delta);
while (!dq.empty() && dq.back().first <= push) {
dq.pop_back();
}
dq.emplace_back(push, ps);
if (ps > c) {
int rem = ps - c - 1;
if (dq.front().second == rem) {
dq.pop_front();
}
}
dp[i] = dq.front().first + (delta * ps);
}
}
if (rev) {
reverse(dp.begin(), dp.end());
}
};
auto Value = [&](vector<long long> x) {
long long res = 0;
for (int i = 0; i < M; ++i) {
res += (i + 1) * x[i];
}
return res;
};
if (Value(pos) - Value(neg) < L) {
swap(pos, neg);
L = -L;
}
debug(L, pos, neg);
for (int i = 0; i < M; ++i) {
L += (i + 1) * neg[i];
banked += neg[i];
}
debug(L, banked);
vector<long long> dec(M);
for (int i = 0; i < M; ++i) {
dec[i] = min(pos[i], L / (i + 1));
L -= dec[i] * (i + 1);
pos[i] -= dec[i];
banked += dec[i];
}
debug(pos, dec, L, banked);
assert(L >= 0);
for (int i = 0; i < M; ++i) {
Push(i + 1, neg[i], -1);
}
for (int i = 0; i < M; ++i) {
Push(i + 1, pos[i], +1);
}
for (int i = 0; i < M; ++i) {
Push(-(i + 1), dec[i], -1);
}
if (dp[L] == -inf) {
cout << "impossible\n";
} else {
cout << banked + dp[L] << '\n';
}
}
