#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll dp[205][205][205][2];
signed main() {
int n, L, ans = 0; cin >> n >> L;
vector<int> p(n+2); p[0] = p[n+1] = L;
vector<int> t(n+2); t[0] = t[n+1] = -1;
for(int i=1; i<=n; i++) cin >> p[i];
for(int i=1; i<=n; i++) cin >> t[i];
auto D = [&](int x, int y) {
return min( abs(x - y), L - abs(x - y) );
};
for(int i=0; i<=n+1; i++)
for(int j=i; j<=n+1; j++)
for(int k=0; k<=n; k++) dp[i][j][k][0] = dp[i][j][k][1] = 1e18;
dp[0][n+1][0][0] = dp[0][n+1][0][1] = 0;
for(int i=0; i<=n+1; i++) {
for(int j=n+1; j>=i+2; j--) {
for(int k=0; k<n; k++) {
ll d = dp[i][j][k][0] + D(p[i], p[i+1]);
int nk = k + (t[i+1] >= d);
dp[i+1][j][nk][0] = min(dp[i+1][j][nk][0], d);
d = dp[i][j][k][1] + D(p[j], p[j-1]);
nk = k + (t[j-1] >= d);
dp[i][j-1][nk][1] = min(dp[i][j-1][nk][1], d);
d = dp[i][j][k][1] + D(p[j], p[i+1]);
nk = k + (t[i+1] >= d);
dp[i+1][j][nk][0] = min(dp[i+1][j][nk][0], d);
d = dp[i][j][k][0] + D(p[i], p[j-1]);
nk = k + (t[j-1] >= d);
dp[i][j-1][nk][1] = min(dp[i][j-1][nk][1], d);
}
}
}
for(int i=0; i<=n+1; i++)
for(int j=i; j<=n+1; j++)
for(int k=0; k<=n; k++)
for(int l : { 0, 1 })
if(dp[i][j][k][l] != 1e18)
ans = max(ans, k);
cout << ans << '\n';
}
