#include <bits/stdc++.h>
#define MAX 205
using namespace std;
long long dp[MAX][MAX][MAX][2];
/// dp[i][j][k][0/1] = timpul minim sa parcurgem primele i clockwise
/// si primele j counterclockwise colectand cel putin k statui
/// si avand 1 (daca ne oprim la al i-lea clockwise)
/// sau 0 (daca ne oprim la al j-lea counterclockwise)
int dist[MAX];
int limit[MAX];
int N,L;
int ans;
void read()
{
cin>>N>>L;
int i;
for(i=1;i<=N;++i)
cin>>dist[i];
for(i=1;i<=N;++i)
cin>>limit[i];
dist[N+1]=L;
dist[N+2]=L;
}
void minself(long long& x,long long y)
{
x=min(x,y);
}
void calc_dp()
{
int i,j,k;
for(i=0;i<=N;++i)
for(j=0;j<=N;++j)
for(k=0;k<=N;++k)
dp[i][j][k][0]=dp[i][j][k][1]=2e18;
dp[0][0][0][0]=0;
dp[0][0][0][1]=0;
for(i=0;i<=N;++i)
for(j=0;j<=N-i;++j)
{
if(!i && !j)
continue;
int totaldist=dist[i]+L-dist[N-j+1];
int dist1=dist[i]-dist[i-1];
int dist0=dist[N-j+2]-dist[N-j+1];
dp[i][j][0][1]=2LL*(L-dist[N-j+1])+dist[i];
dp[i][j][0][0]=2LL*dist[i]+L-dist[N-j+1];
for(k=1;k<=i+j;++k)
{
if(i)
{
minself(dp[i][j][k][1],dp[i-1][j][k][1]+dist1);
if(dp[i-1][j][k-1][1]+dist1<=limit[i])
minself(dp[i][j][k][1],dp[i-1][j][k-1][1]+dist1);
}
if(j)
{
minself(dp[i][j][k][0],dp[i][j-1][k][0]+dist0);
if(dp[i][j-1][k-1][0]+dist0<=limit[N-j+1])
minself(dp[i][j][k][0],dp[i][j-1][k-1][0]+dist0);
}
minself(dp[i][j][k][0],dp[i][j][k][1]+totaldist);
minself(dp[i][j][k][1],dp[i][j][k][0]+totaldist);
}
}
}
void debug()
{
int i,j,k,l;
for(i=0;i<=N;++i)
for(j=0;j<=N;++j)
for(k=0;k<=N;++k)
for(l=0;l<2;++l)
if(dp[i][j][k][l]<2e9)
cout<<dp[i][j][k][l]<<' '<<i<<' '<<j<<' '<<k<<' '<<l<<'\n';
}
void get_answer()
{
int i,j,k,l;
for(i=0;i<=N;++i)
for(j=0;j<=N-i;++j)
for(k=0;k<=i+j;++k)
for(l=0;l<2;++l)
if(dp[i][j][k][l]<2e18)
ans=max(ans,k);
}
void write()
{
cout<<ans;
}
int main()
{
read();
calc_dp();
get_answer();
write();
return 0;
}
