#include <bits/stdc++.h>
using namespace std;
#define int int64_t
const int INF = 1e18;
const int maxn = 205;
int dp[maxn][maxn][maxn][2] = {0};
int a[maxn] = {0};
int t[maxn] = {0};
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
int n,L;
cin >> n >> L;
for(int j =1;j <= n;++j)
{
cin >> a[j];
}
a[n+1] = L;
for(int j =1;j <= n;++j)
{
cin >> t[j];
}
for(int i = 0;i <= n;++i)
{
for(int j = 0;j <= n;++j)
{
for(int k = 0;k <= n;++k)
{
for(int l = 0;l < 2;++l)
dp[i][j][k][l] = INF;
}
}
}
int ans = 0;
for(int lx = 0;lx <= n;++lx)
{
for(int rx = 0;lx+rx <= n;++rx)
{
for(int k = 0;k <= lx+rx;++k)
{
for(int l = 0;l < 2;++l)
{
if(lx == 0 && rx == 0)
dp[lx][rx][k][l] = 0;
else
{
if(l == 0)
{
if(lx != 0)
{
dp[lx][rx][k][l] = min(dp[lx][rx][k][l],dp[lx-1][rx][k][0] + a[lx]-a[lx-1]);
dp[lx][rx][k][l] = min(dp[lx][rx][k][l],dp[lx-1][rx][k][1] + L-a[n-rx+1]+a[lx]);
if(k != 0 && dp[lx-1][rx][k-1][0] + a[lx]-a[lx-1] <= t[lx])
dp[lx][rx][k][l] = min(dp[lx][rx][k][l],dp[lx-1][rx][k-1][0] + a[lx]-a[lx-1]);
if(k != 0 && dp[lx-1][rx][k-1][1] + L-a[n-rx+1]+a[lx] <= t[lx])
dp[lx][rx][k][l] = min(dp[lx][rx][k][l],dp[lx-1][rx][k-1][1] + L-a[n-rx+1]+a[lx]);
}
}
else
{
if(rx != 0)
{
dp[lx][rx][k][l] = min(dp[lx][rx][k][l],dp[lx][rx-1][k][0] + a[lx] + L - a[n-rx+1]);
dp[lx][rx][k][l] = min(dp[lx][rx][k][l],dp[lx][rx-1][k][1] + a[n-rx+2]-a[n-rx+1]);
if(k != 0 && dp[lx][rx-1][k-1][0] + a[lx] + L - a[n-rx+1] <= t[n-rx+1])
dp[lx][rx][k][l] = min(dp[lx][rx][k][l],dp[lx][rx-1][k-1][0] + a[lx] + L - a[n-rx+1]);
if(k != 0 && dp[lx][rx-1][k-1][1] + a[n-rx+2]-a[n-rx+1] <= t[n-rx+1])
dp[lx][rx][k][l] = min(dp[lx][rx][k][l],dp[lx][rx-1][k-1][1] + a[n-rx+2]-a[n-rx+1]);
}
}
}
if(dp[lx][rx][k][l] != INF)
{
// cout << lx << ' ' << rx << ' ' << k << ' ' << l << ' ' << dp[lx][rx][k][l] << "\n";
ans = max(ans,k);
}
}
}
}
}
cout << ans;
return 0;
}
