#include <bits/stdc++.h>
using namespace std;
#define int long long
const int INF = 1e10;
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n,L;
cin >> n >> L;
vector<int> pos(n+2),tim(n+1);
for(int i=1;i<=n;i++)cin>>pos[i];
pos[n+1]=L;
for(int i=1;i<=n;i++)cin>>tim[i];
vector DP(n+1,vector(n+1,vector(2,vector(n+1,INF))));
DP[0][0][0][0]=DP[0][0][1][0]=0;
for(int l=0;l<=n;l++) {
for(int r=0;r<=n-l;r++) {
for(int score=0;score<=n;score++) {
// End at L
if(l) {
if(score and tim[l]>=DP[l-1][r][0][score-1]+pos[l]-pos[l-1]) {
DP[l][r][0][score]=DP[l-1][r][0][score-1]+pos[l]-pos[l-1];
} else {
DP[l][r][0][score]=DP[l-1][r][0][score]+pos[l]-pos[l-1];
}
}
// End at r
if(r) {
if(score and tim[n+1-r]>=DP[l][r-1][1][score-1]+pos[n+2-r]-pos[n+1-r]) {
DP[l][r][1][score]=DP[l][r-1][1][score-1]+pos[n+2-r]-pos[n+1-r];
} else {
DP[l][r][1][score]=DP[l][r-1][1][score]+pos[n+2-r]-pos[n+1-r];
}
}
int dist = pos[l]+L-pos[n+1-r];
DP[l][r][0][score]=min(DP[l][r][0][score],DP[l][r][1][score]+dist);
DP[l][r][1][score]=min(DP[l][r][1][score],DP[l][r][0][score]+dist);
}
}
}
for(int x=n;x>=0;x--) {
for(auto&i:DP) {
for(auto&j:i) {
for(auto&k:j) {
if(k[x]<INF){
cout<<x<<'\n';return 0;
}
}
}
}
}
assert(false);
}
