#include <cstdio>
#include <stdio.h>
#include <stdbool.h>
#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
#include <numeric>
#include <cassert>
#include <random>
#include <chrono>
#include <fstream>
using namespace std;
#define int long long
#define pii pair<int, int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
int k;
int dist(int a, int b){
return min(abs(a-b), k-abs(a-b));
}
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, ans=0;
cin>>n>>k;
vector<pii> vect(n+2, mp(0, LLONG_MIN/2));
vect[n+1].fi=k;
for (int i=1; i<=n; ++i)cin>>vect[i].fi;
for (int i=1; i<=n; ++i)cin>>vect[i].se;
vector<vector<vector<vector<int> > > > dp(n+2, vector<vector<vector<int> > >(n+2, vector<vector<int> >(n+2, vector<int>(2, LLONG_MAX/2))));
dp[0][n+1][0][0]=dp[0][n+1][0][1]=0;
for (int l=0; l<n; ++l)for (int r=n+1; r-1>l; --r)for (int i=0; i<=n; ++i){
int res=min(dp[l][r][i][0]+dist(vect[l].fi, vect[l+1].fi), dp[l][r][i][1]+dist(vect[r].fi, vect[l+1].fi));
if (res<=vect[l+1].se)dp[l+1][r][i+1][0]=min(dp[l+1][r][i+1][0], res);
else dp[l+1][r][i][0]=min(dp[l+1][r][i][0], res);
res=min(dp[l][r][i][1]+dist(vect[r].fi, vect[r-1].fi), dp[l][r][i][0]+dist(vect[l].fi, vect[r-1].fi));
if (res<=vect[r-1].se)dp[l][r-1][i+1][1]=min(dp[l][r-1][i+1][1], res);
else dp[l][r-1][i][1]=min(dp[l][r-1][i][1], res);
}
for (int i=0; i<=n+1; ++i)for (int j=0; j<=n+1; ++j)for (int l=0; l<=n+1; ++l)for (int p=0; p<2; ++p)if (dp[i][j][l][p]!=LLONG_MAX/2)ans=max(ans, l);
cout<<ans;
}
