#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int long long
#define FOR(i, a, b) for (int i = (a); i <= (b); i++)
#define FORD(i, a, b) for (int i = (b); i >= (a); i --)
#define REP(i, a) for (int i = 0; i < (a); ++i)
#define REPD(i, a) for (int i = (a) - 1; i >= 0; --i)
#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
constexpr ll LINF = (1ll << 60);
constexpr int INF = (1ll << 30);
constexpr int Mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
/*
Phu Trong from Nguyen Tat Thanh High School for gifted student
*/
template <class X, class Y>
bool minimize(X &x, const Y &y){
X eps = 1e-9;
if (x > y + eps) {x = y; return 1;}
return 0;
}
template <class X, class Y>
bool maximize(X &x, const Y &y){
X eps = 1e-9;
if (x + eps < y) {x = y; return 1;}
return 0;
}
int nArr, L;
#define MAX 202
int A[MAX], T[MAX];
//min DP[l][r][picked][where] = time
//where = 0: clock wise
//where = 1: counter clock wise
int dp[MAX][MAX][MAX][2];
void process(void){
cin >> nArr >> L;
for (int i = 1; i <= nArr; ++i) cin >> A[i];
for (int i = 1; i <= nArr; ++i) cin >> T[i];
A[nArr + 1] = L;
memset(dp, 0x3f, sizeof dp);
REP(i, 2) dp[0][0][0][i] = 0;
REP(l, nArr) REP(r, nArr) REP(picked, nArr){
if(l + r + 1 > nArr) continue;
int cur = dp[l][r][picked][1];
bool can_pick = 0;
can_pick = (cur + (A[r + 1] - A[r]) <= T[r + 1]);
minimize(dp[l][r + 1][picked + can_pick][1], cur + (A[r + 1] - A[r]));
can_pick = (cur + (A[r] + L - A[nArr - l]) <= T[nArr - l]);
minimize(dp[l + 1][r][picked + can_pick][0], cur + (A[r] + L - A[nArr - l]));
cur = dp[l][r][picked][0];
can_pick = (cur + (A[nArr - l + 1] - A[nArr - l]) <= T[nArr - l]);
minimize(dp[l + 1][r][picked + can_pick][0], cur + (A[nArr - l + 1] - A[nArr - l]));
can_pick = (cur + (L - A[nArr - l + 1] + A[r + 1]) <= T[r + 1]);
minimize(dp[l][r + 1][picked + can_pick][1], cur + (L - A[nArr - l + 1] + A[r + 1]));
}
FORD(picked, 0, nArr) FOR(l, 0, nArr) FOR(r, 0, nArr) REP(where, 2){
if(dp[l][r][picked][where] < INF){
return void(cout << picked);
}
}
}
signed main(){
#define name "Whisper"
cin.tie(nullptr) -> sync_with_stdio(false);
//freopen(name".inp", "r", stdin);
//freopen(name".out", "w", stdout);
process();
return (0 ^ 0);
}
