#include <bits/stdc++.h>
#define err(args...) {}
#ifdef DEBUG
#include "_debug.cpp"
#endif
using namespace std;
using ll = long long;
using ld = long double;
template <typename T> using lim = numeric_limits<T>;
template <typename T> istream& operator>>(istream& is, vector<T>& a) { for(T& x : a) { is >> x; } return is; }
template <typename X, typename Y> istream& operator>>(istream& is, pair<X, Y>& p) { return is >> p.first >> p.second; }
const int N = 200, MAX_T = 201;
int n, l, x[N+2], t[N+2];
int mem[2][N+1][N+1][N+1];
int d(int i, int j) {
return (x[j] - x[i] + l) % l;
}
int opt(bool at_L, int L, int R, int T) {
int& ans = mem[at_L][L][R][T];
if(ans == -1) {
if(L <= R) {
int TL, TR;
ans = max(
((TL = d(at_L ? L - 1 : R + 1, L) + T) <= t[L]) + opt(1, L + 1, R, min(TL, MAX_T)),
((TR = d(R, at_L ? L - 1 : R + 1) + T) <= t[R]) + opt(0, L, R - 1, min(TR, MAX_T))
);
} else {
ans = 0;
}
}
return ans;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> n >> l;
for(int i = 1; i <= n; i++) {
cin >> x[i];
}
for(int i = 1; i <= n; i++) {
cin >> t[i];
}
memset(mem, -1, sizeof mem);
cout << opt(true, 1, n, 0) << endl;
return 0;
}
