#include<bits/stdc++.h>
using namespace std;
#define all(x) (x).begin(), (x).end()
#define sz(x) ( (int)(x).size() )
using LL = long long;
template<class T>
inline bool asMn(T &a, const T &b) { return a > b ? a = b, true : false; }
template<class T>
inline bool asMx(T &a, const T &b) { return a < b ? a = b, true : false; }
inline int nxt(int i, int n) { return i == n - 1 ? 0 : i + 1; }
inline int prv(int i, int n) { return !i ? n - 1 : i - 1; }
const int inf = 1e9 + 100;
mt19937 rng( (uint32_t)chrono::steady_clock::now().time_since_epoch().count() );
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef FourLeafClover
freopen("input", "r", stdin);
#endif // FourLeafCLover
int n, l; cin >> n >> l;
vector<int> x(n), t(n);
for (auto &i : x) cin >> i;
for (auto &i : t) cin >> i;
vector<vector<vector<array<int, 2> > > > f(n + 1, vector<vector<array<int, 2> > >(n + 1, vector<array<int, 2> >(n + 1, array<int, 2>{ inf, inf } ) ) );
f[0][n][n][0] = 0;
for (int nStamp = 0; nStamp < n; ++nStamp) {
for (int i = n; ~i; --i) {
for (int j = n, cnt = 0; (j == n && !cnt) || j < i; j = nxt(j, n + 1), cnt += (j == n) ) {
for (int side = 0; side < 2; ++side) if (f[nStamp][i][j][side] < inf) {
int prvI = prv(i, n + 1), nxtJ = nxt(j, n + 1);
if (!side) {
if (prvI != j) asMn(f[nStamp + (f[nStamp][i][j][side] + (i == n ? l : x[i]) - x[prvI] <= t[prvI])][prvI][j][0],
f[nStamp][i][j][side] + (i == n ? l : x[i]) - x[prvI]);
if (nxtJ != i) asMn(f[nStamp + (f[nStamp][i][j][side] + (i == n ? 0 : l - x[i]) + x[nxtJ] <= t[nxtJ])][i][nxtJ][1],
f[nStamp][i][j][side] + (i == n ? 0 : l - x[i]) + x[nxtJ]);
}
else {
if (prvI != j) asMn(f[nStamp + (f[nStamp][i][j][side] + (j == n ? 0 : x[j]) + l - x[prvI] <= t[prvI])][prvI][j][0],
f[nStamp][i][j][side] + (j == n ? 0 : x[j]) + l - x[prvI]);
if (nxtJ != i) asMn(f[nStamp + (f[nStamp][i][j][side] + x[nxtJ] - (j == n ? 0 : x[j]) <= t[nxtJ])][i][nxtJ][1],
f[nStamp][i][j][side] + x[nxtJ] - (j == n ? 0 : x[j]));
}
}
}
}
}
int ans = 0;
for (int nStamp = 1; nStamp <= n; ++nStamp) {
for (int i = n; ~i; --i) {
for (int j = n, cnt = 0; (j == n && !cnt) || j < i; j = nxt(j, n + 1), cnt += (j == n) ) {
for (int side = 0; side < 2; ++side) if (f[nStamp][i][j][side] < inf) ans = nStamp;
}
}
}
cout << ans << '\n';
return 0;
}
