#include "shortcut.h"
#include<bits/stdc++.h>
using namespace std;
const int maxn = 1e3 + 6;
typedef long long ll;
ll prv[maxn];
ll suf[maxn];
ll cur[maxn];
ll pre_res[maxn];
ll suf_res[maxn];
long long find_shortcut(int n, std::vector<int> l, std::vector<int> d, int c)
{
vector<ll> sum(n , 0);
for(int i = 1 ; i < n ; ++i){
sum[i] = sum[i - 1] + l[i - 1];
}
auto dis = [&](int i , int j){
return sum[j] - sum[i];
};
for(int i = 0 ; i < n ; ++i){
if(i > 0)prv[i] = prv[i - 1] + l[i - 1];
prv[i] = max(prv[i] , (ll)d[i]);
}
for(int i = n - 1 ; i >= 0 ; --i){
if(i + 1 < n)suf[i] = suf[i + 1] + l[i];
suf[i] = max(suf[i] , (ll)d[i]);
}
ll res = 0;
for(int i = 0 ; i < n ; ++i){
for(int j = i + 1 ; j < n ; ++j){
res = max(res , dis(i , j) + d[i] + d[j]);
pre_res[j] = max(pre_res[j] , dis(i , j) + d[i] + d[j]);
suf_res[i] = max(suf_res[i] , dis(i , j) + d[i] + d[j]);
}
}
for(int i = 1 ; i < n ; ++i)pre_res[i] = max(pre_res[i] , pre_res[i - 1]);
for(int i = n - 2 ; i >= 0 ; --i)suf_res[i] = max(suf_res[i] , suf_res[i + 1]);
for(int i = 0 ; i < n ; ++i){
for(int j = i + 1 ; j < n ; ++j){
cur[j] = d[j];
if(dis(i,j) <= c)continue;
ll mx = max(pre_res[i] , suf_res[j]);
cur[i] = prv[i];
cur[j] = suf[j];
for(int k = i ; k <= j ; ++k){
for(int t = k + 1 ; t <= j ; ++t){
mx = max(mx , cur[k] + cur[t] + min(dis(k, t) , dis(i,j) + c - dis(k,t)));
if(mx >= res)break;
}
}
cur[j] = d[j];
res = min(res , mx);
}
}
return res;
}
#ifdef LOCAL
#include <cstdio>
#include <cassert>
#include "shortcut.h"
int main()
{
freopen("A.INP","r",stdin);
freopen("A.OUT","w",stdout);
int n, c;
assert(2 == scanf("%d%d", &n, &c));
std::vector<int> l(n - 1);
std::vector<int> d(n);
for (int i = 0; i < n - 1; i++)
assert(1 == scanf("%d", &l[i]));
for (int i = 0; i < n; i++)
assert(1 == scanf("%d", &d[i]));
long long t = find_shortcut(n, l, d, c);
printf("%lld\n", t);
return 0;
}
#endif // LOCAL
