#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 2e2 + 11;
const int inf = 1e9 + 7;
int x[N], t[N], n, L;
int dp[N][N][2];
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr); cout.tie(nullptr);
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;
vector < vector < vector < int > > > dp(n + 1, vector < vector < int > >(n + 1, vector < int >(2, inf)));
dp[0][0][0] = dp[0][0][1] = 0;
int ans = 0;
for(int k = 1; k <= n; k++){
vector < vector < vector < int > > > ndp(n + 1, vector < vector < int > >(n + 1, vector < int >(2, inf)));
for(int i = 0; i <= n; i++){
for(int j = 0; j <= n - i; j++){
if(i > 0){
int T = dp[i - 1][j][0] + x[n - i + 2] - x[n - i + 1];
if(T <= t[n - i + 1]) ndp[i][j][0] = min(ndp[i][j][0], T);
T = dp[i - 1][j][1] + x[j] + L - x[n - i + 1];
if(T <= t[n - i + 1]) ndp[i][j][0] = min(ndp[i][j][0], T);
}
if(j > 0){
int T = dp[i][j - 1][0] + L - x[n - i + 1] + x[j];
if(T <= t[j]) ndp[i][j][1] = min(ndp[i][j][1], T);
T = dp[i][j - 1][1] + x[j] - x[j - 1];
if(T <= t[j]) ndp[i][j][1] = min(ndp[i][j][1], T);
}
if(i > 0) ndp[i][j][0] = min(ndp[i][j][0], ndp[i - 1][j][0] + x[n - i + 2] - x[n - i + 1]);
if(i > 0) ndp[i][j][0] = min(ndp[i][j][0], ndp[i - 1][j][1] + x[j] + L - x[n - i + 1]);
if(j > 0) ndp[i][j][1] = min(ndp[i][j][1], ndp[i][j - 1][0] + x[j] + L - x[n - i + 1]);
if(j > 0) ndp[i][j][1] = min(ndp[i][j][1], ndp[i][j - 1][1] + x[j] - x[j - 1]);
if(ndp[i][j][1] != inf || ndp[i][j][0] != inf) ans = k;
}
}
dp = ndp;
}
cout << ans;
}
// subete no mono no owari wa sugu ni yattekuru
