// https://oj.uz/problem/view/JOI20_ho_t3?locale=en
#include<bits/stdc++.h>
using namespace std;
#define int long long
// have a dp[N][N][N][2] -> minimum time to collect x stamps, with the furthest right being i and left j
// where right clockwise and left counter-clockwise and wether I'm at the left or right position
// h = 0 -> I'm in the right
const int inf = 1e18;
const int maxn = 201;
int dp[maxn][maxn][maxn][2];
int N, L;
int X[maxn];
int T[maxn];
int ans;
int32_t main()
{
cin >> N >> L;
for(int i = 0; i < N; i++)
{
cin >> X[i];
}
for(int i = 0; i < N; i++)
{
cin >> T[i];
}
for(int i = 0; i <= N; i++) for(int j = 0; j <= N; j++) for(int k = 0; k <= N; k++) for(int h = 0; h < 2; h++) dp[i][j][k][h] = inf;
dp[0][0][0][0] = 0;
dp[0][0][0][1] = 0;
// push dp
for(int i = 0; i <= N; i++)
{
for(int j = 0; i+j <= N; j++)
{
for(int k = 0; k <= i+j; k++)
{
for(int h = 0; h < 2; h++)
{
int t = dp[i][j][k][h];
if(t < 1e15)
{
ans = max(ans, k);
}
else continue;
if(i+j >= N) continue;
int pos;
if(!h)
{
if(i == 0) pos = 0;
else pos = X[i-1];
}
else
{
if(j == 0) pos = 0;
else pos = X[N-j];
}
// cout << "i " << i << " j " << j << " k " << k << " h " << h << " pos " << pos << " t " << t << endl;
// looking at guy X[i] and X[N-j-1]
// move to the right
int rmove;
if(pos > X[i]) rmove = X[i]+L-pos;
else rmove = X[i]-pos;
if(rmove+t <= T[i])
{
dp[i+1][j][k+1][0] = min(dp[i+1][j][k+1][0], rmove+t);
}
dp[i+1][j][k][0] = min(dp[i+1][j][k][0], rmove+t);
// move to the left
int lmove;
if(pos < X[N-j-1]) lmove = L-X[N-j-1]+pos;
else lmove = pos-X[N-j-1];
if(lmove+t <= T[N-j-1])
{
dp[i][j+1][k+1][1] = min(dp[i][j+1][k+1][1], lmove+t);
}
dp[i][j+1][k][1] = min(dp[i][j+1][k][1], lmove+t);
}
}
}
}
cout << ans;
return 0;
}
