#include<bits/stdc++.h>
using namespace std;
#define int long long
#define fr first
#define sc second
#define all(x) (x).begin(), (x).end()
const int MOD = 998244353;
const int MAXN = 2e2 + 5; // MUDAR O LIMITE
const int INF1 = 1e9 + 5;
const long long INF = 1e18 + 5;
int dp[2*MAXN][2*MAXN][MAXN][2];
void solve() {
int n, L;
cin >> n >> L;
vector<int> x(2*MAXN), t(2*MAXN);
for(int i = 1; i <= n; i ++) {
cin >> x[i];
x[i+n+1] = x[i];
}
for(int i = 1; i <= n; i ++) {
cin >> t[i];
t[i+n+1] = t[i];
}
x[0] = 0; t[0] = -1; x[n+1] = 0; t[n+1] = -1;
vector<vector<int>> dist(2*MAXN, vector<int>(2*MAXN));
for(int i = 0; i <= 2*n+1; i++) {
for(int j = 0; j <= 2*n+1; j++) {
dist[i][j] = min((int)abs(x[i] - x[j]), (int)(L - abs(x[i] - x[j])));
}
}
for(int i = 0; i <= 2*n+1; i++) {
for(int j = 0; j <= 2*n+1; j++) {
for(int q = 0; q <= n; q++) {
dp[i][j][q][0] = INF;
dp[i][j][q][1] = INF;
}
}
}
dp[0][0][0][0] = 0;
dp[0][0][0][1] = 0;
dp[n+1][n+1][0][0] = 0;
dp[n+1][n+1][0][1] = 0;
for(int sz = 1; sz <= n+1; sz++) {
for(int l = 0; l <= 2*n+1 - sz + 1; l++) {
for(int q = 0; q <= n; q++) {
int r = l + sz - 1;
if(l < 2*n + 1) dp[l][r][q][0] = min(dp[l][r][q][0], dp[l+1][r][q][0] + dist[l+1][l]);
if(l < 2*n + 1) dp[l][r][q][0] = min(dp[l][r][q][0], dp[l+1][r][q][1] + dist[r][l]);
if(r > 0) dp[l][r][q][1] = min(dp[l][r][q][1], dp[l][r-1][q][1] + dist[r-1][r]);
if(r > 0) dp[l][r][q][1] = min(dp[l][r][q][1], dp[l][r-1][q][0] + dist[l][r]);
if(q >= 1) {
if(l < 2*n + 1 && dp[l+1][r][q-1][0] + dist[l+1][l] <= t[l]) {
if(l < 2*n + 1) dp[l][r][q][0] = min(dp[l][r][q][0], dp[l+1][r][q-1][0] + dist[l+1][l]);
}
if(l < 2*n + 1 &&dp[l+1][r][q-1][1] + dist[r][l] <= t[l]) {
if(l < 2*n + 1) dp[l][r][q][0] = min(dp[l][r][q][0], dp[l+1][r][q-1][1] + dist[r][l]);
}
if(r > 0 && dp[l][r-1][q-1][1] + dist[r-1][r] <= t[r]) {
dp[l][r][q][1] = min(dp[l][r][q][1], dp[l][r-1][q-1][1] + dist[r-1][r]);
}
if(r > 0 && dp[l][r-1][q-1][0] + dist[l][r] <= t[r]) {
dp[l][r][q][1] = min(dp[l][r][q][1], dp[l][r-1][q-1][0] + dist[l][r]);
}
}
}
}
}
int ans = 0;
for(int i = 0; i <= n; i++) {
for(int q = 0; q <= n; q++) {
if(dp[i][i+n][q][0] < INF || dp[i][i+n][q][1] < INF) {
ans = max(ans, q);
}
}
}
cout << ans << "\n";
}
int32_t main() {
ios::sync_with_stdio(false);
cin.tie(NULL);
int tt;
tt = 1;
//cin >> tt;
while(tt--) {
solve();
}
return 0;
}
