///
/// Let the voice of love take you higher!
///
#define _USE_MATH_DEFINES
#define FAST ios::sync_with_stdio(false),cin.tie(0);
#include <bits/stdc++.h>
#define Loop(x, l, r) for(ll x = ll(l); x < ll(r); ++x)
#define LoopR(x, l, r) for(ll x = ll(r)-1; x >= ll(l); --x)
#define all(x) x.begin(), x.end()
#define Kill(x) exit((cout << (x) << '\n', 0))
#define YN(flag) ((flag)? "YES": "NO")
#define F first
#define S second
typedef __int128 ll;
typedef unsigned long long ull;
typedef std::pair<int,int> pii;
typedef std::pair<ll ,ll > pll;
using namespace std;
#define int ll
const int N = 210;
ll dp[2][N][N][N]; // d, cnt, l, r
ll len, _x[N], *x = _x+1;
ll _t[N], *t = _t+1;
int n;
ll dis(int i, int j)
{
if(x[j] < x[i]) swap(i, j);
return min(x[j]-x[i], len-(x[j]-x[i]));
}
bool gd(int i, int j, ll t)
{
//if(dis(i,j)+t <= ::t[j]) cerr << i << ' ' << j << ' ' << t << '\n';
return dis(i,j)+t <= ::t[j];
}
void smin(ll& x, ll y){x = min(x, y);}
signed main()
{
FAST;
long long _n, _len;
cin >> _n >> _len;
n = _n; len = _len;
Loop(i,0,n) {long long z; cin >> z; x[i] = z;}
x[n] = x[0]; x[-1] = x[n-1];
Loop(i,0,n) {long long z; cin >> z; t[i] = z;}
t[n] = t[0]; t[-1] = t[n-1];
ll inf = 1; inf <<= 100;
Loop(a,0,2)Loop(b,0,N)Loop(c,0,N)Loop(d,0,N)
dp[a][b][c][d] = inf;
dp[0][t[0 ]>= x[ 0]][1][n ] = x[ 0];
dp[1][t[0 ]>= x[ 0]][1][n ] = x[ 0];
dp[0][t[n-1]>=len-x[n-1]][0][n-1] = len-x[n-1];
dp[1][t[n-1]>=len-x[n-1]][0][n-1] = len-x[n-1];
LoopR(k,1,n)
{
Loop(l,0,n)
{
int r = l+k;
Loop(cnt,0,n)
{
smin(dp[0][cnt+gd(l-1,l ,dp[0][cnt][l][r])][l+1][r], dp[0][cnt][l][r]+dis(l-1,l ));
smin(dp[1][cnt+gd(l-1,r-1,dp[0][cnt][l][r])][l][r-1], dp[0][cnt][l][r]+dis(l-1,r-1));
smin(dp[0][cnt+gd(r ,l ,dp[1][cnt][l][r])][l+1][r], dp[1][cnt][l][r]+dis(r ,l ));
smin(dp[1][cnt+gd(r ,r-1,dp[1][cnt][l][r])][l][r-1], dp[1][cnt][l][r]+dis(r ,r-1));
}
}
}
int ans = 0;
Loop(i,0,n) Loop(cnt,ans+1,N)
{
if(dp[0][cnt][i][i] != inf) ans = cnt;
if(dp[1][cnt][i][i] != inf) ans = cnt;
}
cout << signed(ans) << '\n';
}
