#include <bits/stdc++.h>
#define ll long long
#define ull unsigned ll
#define pb push_back
#define pa pair<int, int>
#define pall pair<ll, int>
#define fi first
#define se second
#define TASK "test"
#define Size(x) (int) x.size()
#define all(x) x.begin(), x.end()
using namespace std;
template<typename T1, typename T2> bool mini (T1 &a, T2 b) {if(a > b) a = b; else return 0; return 1;}
template<typename T1, typename T2> bool maxi (T1 &a, T2 b) {if(a < b) a = b; else return 0; return 1;}
const int MOD = 1e9 + 7;
const int LOG = 20;
const int maxn = 4e2 + 7;
const ll oo = 1e9 + 69;
int n, l, x[maxn], t[maxn], dp[maxn][maxn][207][2];
int add(int a, int b) {
a += b;
if(a >= l) a -= l;
if(a < 0) a += l;
return a;
}
int dist(int a, int b) {
return min(add(b, -a), add(a, -b));
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
//freopen(TASK".inp", "r", stdin);
//freopen(TASK".out", "w", stdout);
cin>>n>>l;
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[1 + n] = 0;
t[1 + n] = 0;
int ans = 0;
for(int i = 0; i <= n * 2 + 1; i++) {
for(int j = 0; j <= n * 2 + 1; j++) {
for(int k = 0; k <= n; k++) {
for(int t = 0; t < 2; t++) dp[i][j][k][t] = oo;
}
}
}
dp[n + 1][n + 1][0][0] = 0;
dp[n + 1][n + 1][0][1] = 0;
for(int i = 2 * n + 1; i >= 1; i--) {
for(int j = i; j <= 2 * n + 1; j++) {
if(j - i + 1 >= n + 1 || i > n + 1 || j < n + 1) continue;
for(int k = 0; k <= n; k++) {
mini(dp[i][j][k][1], dp[i][j][k][0] + dist(x[j], x[i]));
mini(dp[i][j][k][0], dp[i][j][k][1] + dist(x[i], x[j]));
int nxt = dp[i][j][k][0];
if(i - 1 >= 1) {
nxt += dist(x[i - 1], x[i]);
if(nxt <= t[i - 1] && k + 1 <= n) {
mini(dp[i - 1][j][k + 1][0], nxt);
maxi(ans, k + 1);
}
else mini(dp[i - 1][j][k][0], nxt);
}
nxt = dp[i][j][k][1];
if(j + 1 <= 2 * n + 1) {
nxt += dist(x[j + 1], x[j]);
if(nxt <= t[j + 1] && k + 1 <= n) {
mini(dp[i][j + 1][k + 1][1], nxt);
maxi(ans, k + 1);
}
else mini(dp[i][j + 1][k][1], nxt);
}
}
}
}
cout<<ans;
return 0;
}
