#include <bits/stdc++.h>
#define fi first
#define se second
#define ssize(x) int(x.size())
#define pn printf("\n");
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<int, ll> pil;
typedef pair<ll, int> pli;
typedef pair<ll, ll> pll;
int inf = 1e09; ll infll = 1e18;
struct gr{
vector<vector<pil>> g;
vector<ll> dist;
void init(int n){ g.resize(n), dist.resize(n); }
void prepare(){ fill(dist.begin(), dist.end(), infll); }
void dfs(int x, ll d){
dist[x] = d;
for(pil u : g[x]) if(d+u.se < dist[u.fi]) dfs(u.fi, d+u.se);
}
} gr;
ll find_shortcut(int n, vector<int> d_main, vector<int> d_sec, int c){
gr.init(n<<1);
for(int i = 0; i < n-1; ++i) gr.g[i].emplace_back(i+1, d_main[i]), gr.g[i+1].emplace_back(i, d_main[i]);
for(int i = 0; i < n; ++i) gr.g[i].emplace_back(i+n, d_sec[i]), gr.g[i+n].emplace_back(i, d_sec[i]);
ll result = infll;
vector<int> candidates;
for(int a = 0; a < n-1; ++a)
for(int b = a+1; b < n; ++b){
gr.g[a].emplace_back(b, c), gr.g[b].emplace_back(a, c);
gr.prepare(); gr.dfs(n, 0);
ll d = -1;
for(int i = 0; i < n<<1; ++i) if(gr.dist[i] != infll && d < gr.dist[i]) d = gr.dist[i];
for(int i = 0; i < n<<1; ++i) if(d == gr.dist[i]) candidates.emplace_back(i);
ll tmp_d, tmp_res = ssize(candidates) ? 0 : infll;
for(int i : candidates) {
gr.prepare(), gr.dfs(i, 0);
tmp_d = -1;
for(int j = 0; j < n<<1; ++j) if(gr.dist[j] != infll && tmp_d < gr.dist[j]) tmp_d = gr.dist[j];
tmp_res = max(tmp_res, tmp_d);
}
result = min(result, tmp_res);
gr.g[a].pop_back(), gr.g[b].pop_back();
}
return result;
}
#ifdef LOCAL
int main(){
int n, c; scanf("%d%d", &n, &c);
vector<int> d_main(n), d_sec(n);
for(int i = 0; i < n-1; ++i) scanf("%d", &d_main[i]);
for(int i = 0; i < n; ++i) scanf("%d", &d_sec[i]);
ll result = find_shortcut(n, d_main, d_sec, c);
printf("%lld\n", result);
return 0;
}
#endif
