#include<bits/stdc++.h>
#define int long long
using namespace std;
signed main(){
ios::sync_with_stdio(false);
cin.tie(0);
int n, laenge; cin >> n >> laenge;
vector<int> wo(n+2, 0), zeit(n+2, 0);
for(int i=1; i<=n; i++) cin >> wo[i];
for(int i=1; i<=n; i++) cin >> zeit[i];
wo[n+1] = laenge;
zeit[n+1] = 0;
vector<vector<vector<vector<int>>>> dp(n+2, vector<vector<vector<int>>>(n+2, vector<vector<int>>(n+2, vector<int>(2, 1e18))));
dp[n+1][0][0][1] = 0;
dp[n+1][0][0][0] = 0;
int res = 0;
for(int c=0; c<n; c++){//Anz Marken
for(int l=n+1; l>0; l--){//linkes Ende
for(int r=0; r<l; r++){//rechtes Ende
if(dp[l][r][c][0]!=1e18){//sind am linken Ende
//ans rechte Ende laufen
if(r+1!=l){
int dist = wo[r+1]+laenge-wo[l];
if(dp[l][r][c][0]+dist<=zeit[r+1]){
dp[l][r+1][c+1][1] = min(dp[l][r][c][0] + dist, dp[l][r+1][c+1][1]);
res = max(res, c+1);
}else dp[l][r+1][c][1] = min(dp[l][r+1][c][1], dp[l][r][c][0] + dist);
}
//ans neue linke Ende laufen
if(l-1!=r){
int dist = wo[l]-wo[l-1];
if(dp[l][r][c][0]+dist<=zeit[l-1]){
dp[l-1][r][c+1][0] = min(dp[l-1][r][c+1][0], dp[l][r][c][0] + dist);
res = max(res, c+1);
}else dp[l-1][r][c][0] = min(dp[l-1][r][c][0], dp[l][r][c][0] + dist);
}
}
if(dp[l][r][c][1]!=1e18){//sind am rechten Ende
//ans linke Ende laufen
int dist = wo[r]+laenge-wo[l-1];
if(l-1!=r){
if(dp[l][r][c][1]+dist<=zeit[l-1]){
dp[l-1][r][c+1][0] = min(dp[l-1][r][c+1][0], dp[l][r][c][1] + dist);
res = max(res, c+1);
}else dp[l-1][r][c][0] = min(dp[l-1][r][c][0], dp[l][r][c][1] + dist);
}
//ans neue rechte Ende laufen
dist = wo[r+1]-wo[r];
if(r+1!=l){
if(dp[l][r][c][1]+dist<=zeit[r+1]){
dp[l][r+1][c+1][1] = min(dp[l][r+1][c+1][1], dp[l][r][c][1] + dist);
res = max(res, c+1);
}else dp[l][r+1][c][1] = min(dp[l][r+1][c][1], dp[l][r][c][1] + dist);
}
}
}
}
}
cout << res;
return 0;
}
