#include <bits/stdc++.h>
#define F first
#define S second
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define ALL(v) (v).begin(), (v).end()
#define debug(x) cerr << #x << " " << (x) << endl;
#define V vector
using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef V<int> vi;
const int N = 202, INF = 0x3f3f3f3f;
int x[N], dp[N][N][N][2], t[N];
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
int n, l;
cin >> n >> l;
for(int i = 0; i < n; i++) cin >> x[i];
for(int i = 0; i < n; i++) cin >> t[i];
memset(dp, 0x3f, sizeof dp);
if(x[0] <= t[0]) dp[1][0][1][0] = x[0];
else dp[1][0][0][0] = x[0];
if(l-x[n-1] <= t[n-1]) dp[0][1][1][1] = l-x[n-1];
else dp[0][1][0][1] = l-x[n-1];
for(int i = 0; i <= n; i++) {
for(int j = 0; j + i <= n - 1; j++) {
for(int k = 0; k <= i + j; k++) {
if(dp[i][j][k][0] != INF) {
//cerr << "dp[" << i << "][" << j << "][" << k << "][0] = " << dp[i][j][k][0] << endl;
// 0
if(dp[i][j][k][0] + x[i]-x[i-1] <= t[i])
dp[i + 1][j][k+1][0] = min(dp[i + 1][j][k+1][0], dp[i][j][k][0] + x[i]-x[i-1]);
else
dp[i + 1][j][k][0] = min(dp[i + 1][j][k][0], dp[i][j][k][0] + x[i]-x[i-1]);
// 1
if(dp[i][j][k][0] + x[i - 1] + l - x[n-j-1] <= t[n-j-1])
dp[i][j + 1][k+1][1] = min(dp[i][j + 1][k+1][1], dp[i][j][k][0] + x[i - 1] + l - x[n-j-1]);
else
dp[i][j + 1][k][1] = min(dp[i][j + 1][k][1], dp[i][j][k][0] + x[i - 1] + l - x[n-j-1]);
}
if(dp[i][j][k][1] != INF) {
//cerr << "dp[" << i << "][" << j << "][" << k << "][1] = " << dp[i][j][k][1] << endl;
// 0
if(dp[i][j][k][1] + l-x[n-j]+x[i] <= t[i])
dp[i + 1][j][k+1][0] = min(dp[i + 1][j][k+1][0], dp[i][j][k][1] + l-x[n-j]+x[i]);
else
dp[i + 1][j][k][0] = min(dp[i + 1][j][k][0], dp[i][j][k][1] + l-x[n-j]+x[i]);
// 1
if(dp[i][j][k][1] + x[n-j] - x[n-j-1] <= t[n-j-1])
dp[i][j + 1][k+1][1] = min(dp[i][j + 1][k+1][1], dp[i][j][k][1] + x[n-j] - x[n-j-1]);
else
dp[i][j + 1][k][1] = min(dp[i][j + 1][k][1], dp[i][j][k][1] + x[n-j] - x[n-j-1]);
}
}
}
}
int mx = 0;
for(int i = 0; i <= n; i++)
for(int j = 0; j <= n; j++)
for(int k = 0; k <= i + j; k++) {
if(dp[i][j][k][0] != INF) mx = max(mx, k);
if(dp[i][j][k][1] != INF) mx = max(mx, k);
}
cout << mx << endl;
}
