#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
using ll = long long;
#define int ll
int n,l;
const int INF = (int)4e18;
int dp[200][200][201][2]; // s,e,stamps,l0 r1
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
for(int i = 0; i < 200; i++) for(int j = 0; j < 200; j++) for(int k = 0; k < 201; k++) {
dp[i][j][k][0] = INF;
dp[i][j][k][1] = INF;
}
cin >> n >> l;
vector<int> x(n); for(int i = 0; i < n; i++) cin >> x[i];
vector<int> t(n); for(int i = 0; i < n; i++) cin >> t[i];
for(int i = 0; i < n; i++) {
dp[i][i][0][0] = min(x[i],l-x[i]);
dp[i][i][0][1] = min(x[i],l-x[i]);
if(dp[i][i][0][0]<=t[i]) {
dp[i][i][1][0] = dp[i][i][0][0];
dp[i][i][1][1] = dp[i][i][0][0];
}
}
auto dist = [&](const int& a, const int& b) -> ll {
return min(abs(a-b),l-abs(a-b));
};
for(int len = 2; len <= n; len++) {
for(int s = 0; s < n; s++) {
int e = (s+len-1)%n;
for(int k = 0; k < len; k++) {
//choose l in both cases
int opt = min(dp[(s+1+n)%n][e][k][0]+dist(x[(s+1+n)%n],x[s]),dp[(s+1+n)%n][e][k][1]+dist(x[e],x[s]));
int nk = k + (opt<=t[s]);
dp[s][e][nk][0] = min(dp[s][e][nk][0],opt);
//choose r in both cases
opt = min(dp[s][(e-1+n)%n][k][0]+dist(x[s],x[e]),dp[s][(e-1+n)%n][k][1]+dist(x[(e-1+n)%n],x[e]));
nk = k + (opt<=t[e]);
dp[s][e][nk][1] = min(dp[s][e][nk][1],opt);
}
}
}
int ans = 0;
for(int i = 0; i < 200; i++) for(int j = 0; j < 200; j++) for(int k = 0; k < 201; 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;
}
