#include "bits/stdc++.h"
using namespace std;
const int maxn = 205;
using ll = long long;
ll inf = 1e18;
ll x[maxn], t[maxn];
ll L;
int n;
ll dp[maxn][maxn][maxn][2];
int main(int argc, char const *argv[])
{
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n >> L;
for(int i = 1; i <= n; ++i){
cin >> x[i];
}
for(int i = 1; i <= n; ++i){
cin >> t[i];
}
x[0] = 0;
x[n + 1] = L;
t[n + 1] = -1;
t[0] = -1;
for(int i = 0; i <= n + 1; ++i)for(int j = 0; j <= n + 1; ++j)for(int k = 0; k <= n + 1; ++k)for(int l = 0; l < 2; ++l)dp[i][j][k][l] = inf;
dp[0][n + 1][0][0] = dp[0][n + 1][0][1] = 0;
for(int l = n + 1; l > 1; --l){
for(int i = 0, j = i + l; j <= n + 1; ++i, ++j){
for(int k = 0; k <= n + 1; ++k){
for(int pos = 0; pos < 2; ++pos){
if(pos == 0){
ll mn = dp[i][j][k][pos];
if(t[i + 1] >= mn + llabs(x[i + 1] - x[i])){
dp[i + 1][j][k + 1][pos] = min(dp[i + 1][j][k + 1][pos], mn + llabs(x[i + 1] - x[i]));
}else {
dp[i + 1][j][k][pos] = min(dp[i + 1][j][k][pos], mn + llabs(x[i + 1] - x[i]));
}
if(t[j - 1] >= mn + L - llabs(x[j - 1] - x[i])){
dp[i][j - 1][k + 1][1] = min(dp[i][j - 1][k + 1][1], mn + L - llabs(x[j - 1] - x[i]));
}else {
dp[i][j - 1][k][1] = min(dp[i][j - 1][k][1], mn + L - llabs(x[j - 1] - x[i]));
}
}else {
ll mn = dp[i][j][k][pos];
ll X = mn + L - llabs(x[j] - x[i + 1]);
if(t[i + 1] >= X){
dp[i + 1][j][k + 1][0] = min(dp[i + 1][j][k + 1][0], X);
}else {
dp[i + 1][j][k][0] = min(dp[i + 1][j][k][0], X);
}
X = mn + x[j] - x[j - 1];
if(t[j - 1] >= X){
dp[i][j - 1][k + 1][pos] = min(dp[i][j - 1][k + 1][pos], X);
}else {
dp[i][j - 1][k][pos] = min(dp[i][j - 1][k][pos], X);
}
}
}
}
}
}
int ans = 0;
for(int k = 0; k <= n; ++k){
for(int i = 0; i <= n + 1; ++i){
for(int j = i + 1; j <= n + 1; ++j){
for(int pos = 0; pos < 2; ++pos){
if(dp[i][j][k][pos] < inf){
ans = max(ans, k);
}
}
}
}
}
cout << ans << '\n';
return 0;
}
