#include <bits/stdc++.h>
using namespace std;
typedef long long llong;
const llong inf = 1e18;
int n, L;
int X[202], T[202];
llong dp[202][202][202];
int dist(int x, int y) {
int ret = abs(X[x] - X[y]);
return min(ret, L - ret);
}
llong get(int x, int y, int c) {
if (c < 0) return inf;
if (x < 0 || x > n + 1) return inf;
if (y < 0 || y > n + 1) return inf;
if (dp[c][x][y] != -1) return dp[c][x][y];
llong ret = inf;
int px = x;
if (x < y) --px; else ++px;
ret = min(ret, get(px, y, c) + dist(px, x));
ret = min(ret, get(y, px, c) + dist(y, x));
if (get(px, y, c - 1) + dist(px, x) <= T[x]) ret = min(ret, get(px, y, c - 1) + dist(px, x));
if (get(y, px, c - 1) + dist(y, x) <= T[x]) ret = min(ret, get(y, px, c - 1) + dist(y, x));
return dp[c][x][y] = ret;
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n >> L;
for (int i = 1; i <= n; ++i) cin >> X[i]; X[n + 1] = L;
for (int i = 1; i <= n; ++i) cin >> T[i]; T[0] = T[n + 1] = -1;
memset(dp, -1, sizeof(dp));
dp[0][0][n + 1] = 0;
dp[0][n + 1][0] = 0;
for (int i = 1; i <= n; ++i) dp[i][0][n + 1] = dp[i][n + 1][0] = inf;
for (int ans = n; ans > 0; --ans) {
for (int i = 1; i <= n; ++i) {
if (get(i - 1, i, ans) < inf || get(i, i - 1, ans) < inf) {
printf("%d\n", ans);
return 0;
}
}
}
printf("0\n");
return 0;
}
