#include "bits/stdc++.h"
using namespace std;
#define ar array
const int N = 205;
int dp[2][N][N][N];
int x[N], t[N];
signed main(){
ios::sync_with_stdio(0); cin.tie(0);
int n, L; cin>>n>>L;
for(int i=1;i<=n;i++) cin>>x[i];
for(int i=1;i<=n;i++) cin>>t[i];
x[n + 1] = L;
memset(dp, 127, sizeof dp);
int MX = dp[0][0][0][0];
dp[0][0][n+1][0] =
dp[1][0][n+1][0] = 0;
int res = 0;
for(int c=0;c<=n;c++){
for(int l=0;l<=n;l++){
for(int r=n+1;r>l;r--){
dp[0][l][r][c] = min(dp[0][l][r][c], dp[1][l][r][c] + L - x[r] + x[l]);
dp[1][l][r][c] = min(dp[1][l][r][c], dp[0][l][r][c] + L - x[r] + x[l]);
if(dp[0][l][r][c] < MX) res = max(res, c);
if(dp[1][l][r][c] < MX) res = max(res, c);
//~ if(l == 0 && r == 1){
//~ cout<<l<<" "<<r<<" "<<c<<" "<<dp[0][l][r][c]<<" "<<dp[1][l][r][c]<<"\n";
//~ }
dp[0][l+1][r][c] = min(dp[0][l+1][r][c], dp[0][l][r][c] + x[l+1] - x[l]);
if(dp[0][l][r][c] + x[l+1] - x[l] <= t[l+1]){
dp[0][l+1][r][c+1] = min(dp[0][l+1][r][c+1], dp[0][l][r][c] + x[l+1] - x[l]);
}
dp[1][l][r-1][c] = min(dp[1][l][r-1][c], dp[1][l][r][c] + x[r] - x[r-1]);
if(dp[1][l][r][c] + x[r] - x[r-1] <= t[r-1]){
dp[1][l][r-1][c+1] = min(dp[1][l][r-1][c+1], dp[1][l][r][c] + x[r] - x[r-1]);
}
}
}
}
cout<<res<<"\n";
}
