#include <iostream>
#include <algorithm>
using namespace std;
template<class T> T &chmin(T &a,const T &b){ return a = min(a,b); }
template<class T> T &chmax(T &a,const T &b){ return a = max(a,b); }
using ll = long long;
const ll INF = 1e18;
ll dp[210][210][2][210];
signed main(){
int n;
ll l,x[210] = {},t[210];
cin >> n >> l;
for(int i = 0;i < n;i++) cin >> x[i + 1];
for(int i = 0;i < n;i++) cin >> t[i + 1];
x[n + 1] = l;
for(int i = 0;i <= n + 1;i++){
for(int j = 0;j <= n + 1;j++){
for(int k = 0;k < 2;k++){
for(int m = 0;m <= n;m++) dp[i][j][k][m] = INF;
}
}
}
dp[0][n + 1][0][0] = dp[0][n + 1][1][0] = 0;
for(int i = 0;i < n;i++){
for(int j = n + 1;j >= i + 2;j--){
for(int m = 0;m <= n;m++){
ll tim = min(dp[i][j][0][m]+x[i+1]-x[i],dp[i][j][1][m]+l-x[j]+x[i+1]);
chmin(dp[i + 1][j][0][m + (tim <= t[i + 1])],tim);
tim = min(dp[i][j][0][m]+l-x[j-1]+x[i],dp[i][j][1][m]+x[j]-x[j-1]);
chmin(dp[i][j - 1][1][m + (tim <= t[j - 1])],tim);
}
}
}
int ans = 0;
for(int i = 0;i <= n + 1;i++){
for(int j = 0;j <= n + 1;j++){
for(int k = 0;k < 2;k++){
for(int m = 0;m <= n;m++){
if(dp[i][j][k][m] != INF) chmax(ans,m);
}
}
}
}
cout << ans << endl;
}
