#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define sp ' '
#define en '\n'
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
using namespace std;
const int N = 200 + 2;
const ll linf = 1e18;
ll dp[N][N][N][2];
int a[N], b[N];
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n, L;
cin >> n >> L;
for (int i = 1; i <= n; i++) cin >> a[i];
for (int i = 1; i <= n; i++) cin >> b[i];
a[n + 1] = L;
for (int i = 0; i < N; i++) {
for (int j = 0; j < N; j++) {
for (int k = 0; k < N; k++) {
dp[i][j][k][0] = dp[i][j][k][1] = linf;
}
}
}
dp[0][0][0][0] = dp[0][0][0][1] = 0;
for (int i = 0; i <= n; i++) {
for (int j = 0; j <= n - i; j++) {
for (int k = 0; k <= i + j; k++) {
if (i > 0) {
smin(dp[i][j][k][0], dp[i - 1][j][k][1] + L - a[n - j + 1] + a[i]);
if (k > 0 && dp[i - 1][j][k - 1][1] + L - a[n - j + 1] + a[i] <= b[i])
smin(dp[i][j][k][0], dp[i - 1][j][k - 1][1] + L - a[n - j + 1] + a[i]);
smin(dp[i][j][k][0], dp[i - 1][j][k][0] + a[i] - a[i - 1]);
if (k > 0 && dp[i - 1][j][k - 1][0] + a[i] - a[i - 1] <= b[i])
smin(dp[i][j][k][0], dp[i - 1][j][k - 1][0] + a[i] - a[i - 1]);
}
if (j > 0) {
smin(dp[i][j][k][1], dp[i][j - 1][k][0] + L - a[n - j + 1] + a[i]);
if (k > 0 && dp[i][j - 1][k - 1][0] + L - a[n - j + 1] + a[i] <= b[n - j + 1])
smin(dp[i][j][k][1], dp[i][j - 1][k - 1][0] + L - a[n - j + 1] + a[i]);
smin(dp[i][j][k][1], dp[i][j - 1][k][1] - a[n - j + 1] + a[n - j + 2]);
if (k > 0 && dp[i][j - 1][k - 1][1] - a[n - j + 1] + a[n - j + 2] <= b[n - j + 1])
smin(dp[i][j][k][1], dp[i][j - 1][k - 1][1] - a[n - j + 1] + a[n - j + 2]);
}
}
}
}
int ans = 0;
for (int i = 0; i <= n; i++) {
for (int j = 0; j <= n - i; j++) {
for (int k = 0; k <= i + j; k++) {
if (dp[i][j][k][0] != linf) smax(ans, k);
if (dp[i][j][k][1] != linf) smax(ans, k);
}
}
}
cout << ans << en;
return 0;
}
