#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define mp make_pair
#define int long long
#define sz(a) (int)a.size()
const int mxN = (int)2e2+10;
const int LINF = (int)2e18;
int dp[mxN][mxN][mxN][2];
int x[mxN], t[mxN];
//dp[pref][suf][]
int32_t main() {
ios_base::sync_with_stdio(false); cin.tie(0);
int n, L; cin >> n >> L; int ans = 0;
for(int i = 1; i <= n; i++) cin >> x[i], x[n+i+1]=x[i];
for(int i = 1; i <= n; i++) cin >> t[i], t[n+i+1]=t[i];
for(int i = 0; i < mxN; i++)
for(int j = 0; j < mxN; j++)
for(int k = 0; k < mxN; k++)
for(int l = 0; l < 2; l++)
dp[i][j][k][l] = LINF;
dp[n+1][n+1][0][0]=dp[n+1][n+1][0][1]=0;
//0 1 2 3 4 5 6
t[n+1] = -LINF;
for(int len = 2; len <= n+1; len++){
for(int l = 1; l <= n+1; l++){
for(int k = 0; k <= n; k++){
int r = l+len-1;
dp[l][r][k][0] = min({ dp[l][r][k][0],
dp[l+1][r][k][0]+min(abs(x[l+1]-x[l]),L-abs(x[l+1]-x[l])),
dp[l+1][r][k][1]+min(abs(x[r]-x[l]),L-abs(x[r]-x[l]))
});
dp[l][r][k][1] = min({ dp[l][r][k][1],
dp[l][r-1][k][0]+min(abs(x[l]-x[r]),L-abs(x[l]-x[r])),
dp[l][r-1][k][1]+min(abs(x[r-1]-x[r]),L-abs(x[r-1]-x[r]))
});
if(k){
int tm = abs(x[l+1]-x[l]); tm=min(tm,L-tm); tm+=dp[l+1][r][k-1][0];
if(tm<=t[l]) dp[l][r][k][0] = min(dp[l][r][k][0], tm);
tm = abs(x[r]-x[l]); tm=min(tm,L-tm); tm+=dp[l+1][r][k-1][1];
if(tm<=t[l]) dp[l][r][k][0] = min(dp[l][r][k][0], tm);
tm = abs(x[l]-x[r]); tm=min(tm,L-tm); tm+=dp[l][r-1][k-1][0];
if(tm<=t[r]) dp[l][r][k][1] = min(dp[l][r][k][1],tm);
tm = abs(x[r-1]-x[r]); tm=min(tm,L-tm); tm+=dp[l][r-1][k-1][1];
if(tm<=t[r]) dp[l][r][k][1] = min(dp[l][r][k][1],tm);
}
if(len==n+1 and (dp[l][r][k][0]<LINF or dp[l][r][k][1]<LINF)) ans = max(ans, k);
}
}
}
cout << ans;
}
