//#include<i_am_noob_orz>
#include<bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
#define ll long long
#define int ll
#define ull unsigned long long
#define pii pair<int,int>
#define X first
#define Y second
#define mod ((ll)1e9+7)
#define pb push_back
#define mp make_pair
#define abs(x) ((x)>0?(x):(-(x)))
#define F(n) Fi(i,n)
#define Fi(i,n) Fl(i,0,n)
#define Fl(i,l,n) for(int i=l;i<n;i++)
#define memres(a) memset(a,0,sizeof(a))
#define all(a) a.begin(),a.end()
#define sz(a) ((int)a.size())
#define ceiling(a,b) (((a)+(b)-1)/(b))
#define endl '\n'
#define bit_count(x) __builtin_popcountll((x))
#define ykh mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define jimmy_is_kind false
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> rbtree;
//#define LOCAL
#ifdef LOCAL
#define bug(...) cerr<<"#"<<__LINE__<<' '<<#__VA_ARGS__<<"- ", _do(__VA_ARGS__)
template<typename T> void _do(T && x) {cerr<<x<<endl;}
template<typename T, typename ...S> void _do(T && x, S&&...y) {cerr<<x<<", "; _do(y...);}
#define IOS()
#else
#define IOS() ios_base::sync_with_stdio(0), cin.tie(0)
#define endl '\n'
#define bug(...)
#endif
int add(int a,int b){return(a+b>=mod?a+b-mod:a+b);}
int sub(int a,int b){return(a<b?a+mod-b:a-b);}
int po(int a,int b){
if(b==0)return 1;
if(b==1)return(a%mod);
int tem=po(a,b/2);
if(b&1)return(((tem*tem)%mod)*a)%mod;
else return(tem*tem)%mod;
}
int GCD(int a,int b){
int x=0;
int ra,rb;
while(a&&b){
if(((a&1)==0)&&((b&1)==0)){
a>>=1,b>>=1,x++;
}
else if((a^b)&1){
if(a&1)b>>=1;
else a>>=1;
}
else{
ra=abs(a-b),rb=min(a,b);
a=ra,b=rb;
}
}
return max(a,b)<<x;
}
int gcd(int a,int b){if(b==0)return a;return gcd(b,a%b);}
int n,l,a[205],b[205],dp[205][205][205][2];
signed main(){
IOS();
cin>>n>>l;
F(n)cin>>a[i+1];
F(n)cin>>b[i+1];
int ans=0;
F(n+1)Fi(j,n+1)Fi(l,n+1)dp[i][j][l][0]=dp[i][j][l][1]=1e15;
dp[0][0][0][0]=dp[0][0][0][1]=0;
for(int i=0;i<n;i++){
for(int j=0;j<=i;j++){
for(int k=0;k<=i;k++){
if(i==j){
dp[n][j][k][0]=min(dp[n][j][k][0],dp[0][j][k][0]+l-a[n]);
if(dp[0][j][k][0]+l-a[n]<=b[n])dp[n][j][k+1][0]=min(dp[n][j][k+1][0],dp[0][j][k][0]+l-a[n]);
dp[n][j][k][0]=min(dp[n][j][k][0],dp[0][j][k][1]+a[j]+l-a[n]);
if(dp[0][j][k][1]+a[j]+l-a[n]<=b[n])dp[n][j][k+1][0]=min(dp[n][j][k+1][0],dp[0][j][k][1]+a[j]+l-a[n]);
dp[0][j+1][k][1]=min(dp[0][j+1][k][1],dp[0][j][k][0]+a[j+1]);
if(dp[0][j][k][0]+a[j+1]<=b[j+1])dp[0][j+1][k+1][1]=min(dp[0][j+1][k+1][1],dp[0][j][k][0]+a[j+1]);
dp[0][j+1][k][1]=min(dp[0][j+1][k][1],dp[0][j][k][1]+a[j+1]-a[j]);
if(dp[0][j][k][1]+a[j+1]-a[j]<=b[j+1])dp[0][j+1][k+1][1]=min(dp[0][j+1][k+1][1],dp[0][j][k][1]+a[j+1]-a[j]);
continue;
}
dp[n-i+j][j][k][0]=min(dp[n-i+j][j][k][0],dp[n-i+j+1][j][k][0]+a[n-i+j+1]-a[n-i+j]);
if(dp[n-i+j+1][j][k][0]+a[n-i+j+1]-a[n-i+j]<=b[n-i+j])dp[n-i+j][j][k+1][0]=min(dp[n-i+j][j][k+1][0],dp[n-i+j+1][j][k][0]+a[n-i+j+1]-a[n-i+j]);
dp[n-i+j][j][k][0]=min(dp[n-i+j][j][k][0],dp[n-i+j+1][j][k][1]+a[j]+l-a[n-i+j]);
if(dp[n-i+j+1][j][k][1]+a[j]+l-a[n-i+j]<=b[n-i+j])dp[n-i+j][j][k+1][0]=min(dp[n-i+j][j][k+1][0],dp[n-i+j+1][j][k][1]+a[j]+l-a[n-i+j]);
dp[n-i+j+1][j+1][k][1]=min(dp[n-i+j+1][j+1][k][1],dp[n-i+j+1][j][k][0]+l-a[n-i+j+1]+a[j+1]);
if(dp[n-i+j+1][j][k][0]+l-a[n-i+j+1]+a[j+1]<=b[j+1])dp[n-i+j+1][j+1][k+1][1]=min(dp[n-i+j+1][j+1][k+1][1],dp[n-i+j+1][j][k][0]+l-a[n-i+j+1]+a[j+1]);
dp[n-i+j+1][j+1][k][1]=min(dp[n-i+j+1][j+1][k][1],dp[n-i+j+1][j][k][1]+a[j+1]-a[j]);
if(dp[n-i+j+1][j][k][1]+a[j+1]-a[j]<=b[j+1])dp[n-i+j+1][j+1][k+1][1]=min(dp[n-i+j+1][j+1][k+1][1],dp[n-i+j+1][j][k][1]+a[j+1]-a[j]);
}
}
}
F(n+1)Fi(j,n+1)Fi(k,n+1){
if(dp[i][j][k][0]<1e14)ans=max(ans,k);
if(dp[i][j][k][1]<1e14)ans=max(ans,k);
}
cout<<ans<<endl;
return 0;
}
