#pragma GCC optimize ("Ofast")
#pragma GCC optimize ("unroll-loops")
#include <iostream>
#include <queue>
#include <tuple>
using namespace std;
#define ll long long
#define INF 1e17
int ans;
int n, L;
ll x[205], t[205];
ll dp[2][205][205][205];
bool status[2][205][205][205];
queue<tuple<int, int, int, int>> q;
int main()
{
ios::sync_with_stdio(0);
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];
for(int i = 0; i < 2; i++)
for(int ii = 0; ii <= n; ii++)
for(int iii = 0; iii <= n; iii++)
for(int iv = 0; iv <= n; iv++)
dp[i][ii][iii][iv] = INF;
if(L-x[n] <= t[n])
{
dp[0][n-1][1][1] = L-x[n];
status[0][n-1][1][1] = 1;
q.push({0, n-1, 1, 1});
}
else
{
dp[0][n-1][1][0] = L-x[n];
status[0][n-1][1][0] = 1;
q.push({0, n-1, 1, 0});
}
if(x[1] <= t[1])
{
dp[1][n][2][1] = x[1];
status[1][n][2][1] = 1;
q.push({1, n, 2, 1});
}
else
{
dp[1][n][2][0] = x[1];
status[1][n][2][0] = 1;
q.push({1, n, 2, 0});
}
while(1)
{
bool ok = 0;
int sz = (int)q.size();
while(sz--)
{
ok = 1;
int type, l, r, cnt;
tie(type, l, r, cnt) = q.front(); q.pop();
ans = max(ans, cnt);
if(l < r)
continue;
int cur = (type ? r-1 : l+1);
int pp = (dp[type][l][r][cnt]+(x[cur]-x[l]+L)%L <= t[l]);
dp[0][l-1][r][cnt+pp] = min(dp[0][l-1][r][cnt+pp], dp[type][l][r][cnt]+(x[cur]-x[l]+L)%L);
if(!status[0][l-1][r][cnt+pp])
{
status[0][l-1][r][cnt+pp] = 1;
q.push({0, l-1, r, cnt+pp});
}
pp = (dp[type][l][r][cnt]+(x[r]-x[cur]+L)%L <= t[r]);
dp[1][l][r+1][cnt+pp] = min(dp[1][l][r+1][cnt+pp], dp[type][l][r][cnt]+(x[r]-x[cur]+L)%L);
if(!status[1][l][r+1][cnt+pp])
{
status[1][l][r+1][cnt+pp] = 1;
q.push({1, l, r+1, cnt+pp});
}
}
if(!ok)
break;
}
cout << ans << '\n';
}
