#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
constexpr int SIZE = (1e+5);
ll Items[SIZE];
ll L[SIZE];
int n; ll m;
ll binary(ll target, ll level, ll items) {
ll lo = 0, hi = target;
while (lo <= hi) {
ll mid = lo + (hi - lo) / 2;
ll required_items = mid * (2 * level + mid - 1) / 2;
if (required_items <= items) {
lo = mid + 1;
} else {
hi = mid - 1;
}
}
return hi;
}
void sol() {
long long lo = 1;
long long hi = (1e12);
long long ans = -1;
while (lo <= hi) {
ll mid = lo + (hi - lo) / 2;
ll cost = 0;
ll tmp = m;
bool can_make_triangle = true;
for (int i = 0; i < n; i++) {
if (mid > L[i]) {
ll K = binary(mid - L[i], L[i], Items[i]) + L[i];
if (K < mid) {
if (tmp >= (mid - K)){
tmp -= (mid - K);
}
else{
can_make_triangle = false;
break;
}
}
} else if (mid < L[i]) {
can_make_triangle = false;
break;
}
}
if (can_make_triangle) {
ans = mid;
lo = mid + 1;
} else {
hi = mid - 1;
}
}
if (ans > 0) {
cout << ans << '\n';
} else {
cout << "-1\n";
}
}
int main(void) {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin >> n >> m;
for (int i = 0; i < n; i++) {
cin >> L[i];
}
for (int i = 0; i < n; i++) {
cin >> Items[i];
}
sol();
return 0;
}