#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define MASK(i) (1LL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
#define block_of_code if(true)
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){return __gcd(a, b);}
ll lcm(ll a, ll b){return a / gcd(a, b) * b;}
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ll mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
double rngesus_d(double l, double r){
double cur = rngesus(0, MASK(60) - 1);
cur /= MASK(60) - 1;
return l + cur * (r - l);
}
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if (a < b) {a = b; return true;}
return false;
}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if (a > b) {a = b; return true;}
return false;
}
template <class T>
void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
for(auto item: container) out << item << separator;
out << finish;
}
template <class T>
void remove_dup(vector<T> &a){
sort(ALL(a));
a.resize(unique(ALL(a)) - a.begin());
}
const int N = 205;
const ll INF = 1e18 + 69;
int n, l;
ll dp[N][N][N][2];
int x[N], t[N];
ll dis_on_circle(ll a, ll b){
return min((b - a + l) % l, (a - b + l) % l);
}
int main(void){
ios::sync_with_stdio(0);cin.tie(0); cout.tie(0);
clock_t start = clock();
cin >> n >> l;
for(int i= 0; i<n; ++i)
cin >> x[i];
for(int j= 0; j<n; ++j)
cin >> t[j];
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] = INF;
dp[1][0][x[0] <= t[0]][0] = x[0];
dp[0][1][(l - x[n-1]) <= t[n-1]][1] = l - x[n-1];
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){
for(int z = 0; z <= 1; ++z) if (dp[i][j][k][z] != INF){
ll val = dp[i][j][k][z];
// cout << i << " " << j << " " << k << " " << z << " " << val << "\n";
maximize(ans, k);
if (z == 0) {
if (i + j < n){
ll nxt_val1 = val + dis_on_circle(x[i], x[i-1]);
minimize(dp[i+1][j][k + (nxt_val1 <= t[i])][0], nxt_val1);
ll nxt_val2 = val + dis_on_circle(x[i-1], x[n- j - 1]);
minimize(dp[i][j+1][k + (nxt_val2 <= t[n-j-1])][1], nxt_val2);
}
}
else {
if (i + j < n){
ll nxt_val1 = val + dis_on_circle(x[n-j], x[i]);
minimize(dp[i+1][j][k + (nxt_val1 <= t[i])][0], nxt_val1);
ll nxt_val2 = val + dis_on_circle(x[n-j], x[n- j - 1]);
minimize(dp[i][j+1][k + (nxt_val2 <= t[n-j-1])][1], nxt_val2);
}
}
}
}
cout << ans << "\n";
cerr << "Time elapsed: " << clock() - start << " ms\n";
return 0;
}
