#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 201;
ll dp[2][N][N][N];
int L[N], R[N], TR[N], TL[N];
void ckmin(ll &a, ll b) {
if (a == -1 || a > b) {
a = b;
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n, p;
cin >> n >> p;
for (int i = 0; i < n; ++i) {
cin >> R[i];
L[n - i - 1] = p - R[i];
}
for (int i = 0; i < n; ++i) {
cin >> TR[i];
TL[n - i - 1] = TR[i];
}
memset(dp, -1, sizeof(dp));
//0 - in the left, 1 - in the right
if (R[0] <= TR[0]) {
dp[1][0][1][1] = R[0];
} else {
dp[1][0][1][0] = R[0];
}
if (L[0] <= TL[0]) {
dp[0][1][0][1] = L[0];
} else {
dp[0][1][0][0] = L[0];
}
for (int sum = 1; sum < n; ++sum) {
for (int f = 0; f <= sum; ++f) {
int s = sum - f;
for (int cnt = 0; cnt <= n; ++cnt) {
if (dp[0][f][s][cnt] != -1) {
assert(f);
ll t = dp[0][f][s][cnt];
ll dist = L[f] - L[f - 1] + t;
ckmin(dp[0][f + 1][s][cnt + (dist <= TL[f])], dist);
dist = R[s] + L[f - 1] + t;
ckmin(dp[1][f][s + 1][cnt + (dist <= TR[s])], dist);
}
if (dp[1][f][s][cnt] != -1) {
assert(s);
ll t = dp[1][f][s][cnt];
ll dist = R[s - 1] + L[f] + t;
ckmin(dp[0][f + 1][s][cnt + (dist <= TL[f])], dist);
dist = t + R[s] - R[s - 1];
ckmin(dp[1][f][s + 1][cnt + (dist <= TR[s])], dist);
}
}
}
}
for (int cnt = n; cnt >= 0; --cnt) {
for (int sum = n; sum > 0; --sum) {
for (int f = 0; f <= sum; ++f) {
int s = sum - f;
if (dp[0][f][s][cnt] != -1 || dp[1][f][s][cnt] != -1) {
cout << cnt;
return 0;
}
}
}
}
cout << 0;
return 0;
}
