#include <bits/stdc++.h>
#define ll long long
using namespace std;
ll dp[205][205][205][2];
int X[205],T[205];
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int N,L; cin >> N >> L;
for(int i = 1;i<=N;++i){
cin >> X[i];
}
X[N+1] = L;
for(int i = 1;i<=N;++i){
cin >> T[i];
}
int ans = 0;
memset(dp,0x3f,sizeof(dp));
ll INF = dp[0][0][0][0];
dp[0][0][0][0] = dp[0][0][0][1] = 0;
for(int l = 0;l<=N;++l){
for(int r = 0;r<=N;++r){
if(l+r >= N) break;
for(int k = 0;k<=l+r;++k){
ll tmp = dp[l][r][k][0];
if(tmp <= INF){
dp[l+1][r][k+(tmp+X[N-l+1]-X[N-l] <= T[N-l])][0] = min(dp[l+1][r][k+(tmp+X[N-l+1]-X[N-l] <= T[N-l])][0],tmp+X[N-l+1]-X[N-l]);
dp[l][r+1][k+(tmp+L-X[N-l+1]+X[r+1] <= T[r+1])][1] = min(dp[l][r+1][k+(tmp+L-X[N-l+1]+X[r+1] <= T[r+1])][1],tmp+L-X[N-l+1]+X[r+1]);
}
tmp = dp[l][r][k][1];
if(tmp <= INF){
dp[l+1][r][k+(tmp+L-X[N-l]+X[r]<=T[N-l])][0] = min(dp[l+1][r][k+(tmp+L-X[N-l]+X[r]<=T[N-l])][0],tmp+L-X[N-l]+X[r]);
dp[l][r+1][k+(tmp+X[r+1]-X[r]<=T[r+1])][1]=min(dp[l][r+1][k+(tmp+X[r+1]-X[r]<=T[r+1])][1],tmp+X[r+1]-X[r]);
}
}
}
}
for(int i = 0;i<=N;++i){
for(int j = 0;j<=N;++j){
for(int k = 0;k<=N;++k){
if(dp[i][j][k][0] != INF){
ans = max(ans,k);
}
if(dp[i][j][k][1] != INF){
ans = max(ans,k);
}
}
}
}
cout << ans << "\n";
return 0;
}
