#include <bits/stdc++.h>
using namespace std;
const int inf = 1e9 + 99;
const int Nmax = 205;
int dp[Nmax][Nmax][Nmax][2];
int n, L, d[Nmax], t[Nmax];
int ans = 0;
void min_to(int &x, int y)
{
if(x > y) x = y;
}
int main()
{
// freopen("input", "r", stdin);
cin.sync_with_stdio(false); cin.tie(0);
cin >> n >> L;
int i, j, k;
for(i=1; i<=n; ++i) cin >> d[i];
for(i=1; i<=n; ++i) cin >> t[i];
d[0] = 0; d[n+1] = L;
for(i=0; i<=n+1; ++i)
for(j=0; j<=n+1;++j)
for(k=0; k<=n+1; ++k)
dp[i][j][k][0] = dp[i][j][k][1] = inf;
dp[n+1][0][0][0] = dp[n+1][0][0][1] = 0;
for(i=n+1; i; --i)
for(j=0; j<i; ++j)
for(k=0; k<=n; ++k)
{
int tmp;
// if(i == 4) exit(0);
if(dp[i][j][k][0] < inf)
{
/// 0, j -> j+1
if(j + 1 < i)
{
tmp = dp[i][j][k][0] + (d[j+1] - d[j]);
min_to(dp[i][j+1][k + (tmp <= t[j+1])][0], tmp);
}
/// 0, i->i-1
if(j < i-1)
{
tmp = dp[i][j][k][0] + d[j] + (L - d[i-1]);
min_to(dp[i-1][j][k + (tmp <= t[i-1])][1], tmp);
}
ans = max(ans, k);
// cerr << i << ' ' << j << ' ' << k << ' ' << 0 << ' ' << dp[i][j][k][0] << '\n';
}
if(dp[i][j][k][1] < inf)
{
/// 1, i->i-1
if(j < i-1)
{
tmp = dp[i][j][k][1] + (d[i] - d[i-1]);
min_to(dp[i-1][j][k + (tmp <= t[i-1])][1], tmp);
}
/// 1, j->j+1
if(j + 1 < i)
{
tmp = dp[i][j][k][1] + (L - d[i]) + d[j+1];
min_to(dp[i][j+1][k + (tmp <= t[j+1])][0], tmp);
}
ans = max(ans, k);
// cerr << i << ' ' << j << ' ' << k << ' ' << 1 << ' ' << dp[i][j][k][1] << '\n';
}
}
cout << ans << '\n';
return 0;
}
