#include <iostream>
using namespace std;
const long long INF = 1e18;
int main(){
int n;
long long L;
cin >> n >> L;
long long a[n], b[n];
for (int i = 0; i < n; i++){
cin >> a[i];
}
for (int i = 0; i < n; i++){
cin >> b[i];
}
auto idx = [&](int i) -> int {
return (i % n + n) % n;
};
auto dis = [&](long long x, long long y) -> long long {
if (x > y) swap(x, y);
return min(y - x, x + L - y);
};
long long dp[n][n][n + 1][2]{}; // [l, r], pickcnt, cur(l, r) => min time
fill_n(&dp[0][0][0][0], sizeof(dp) / sizeof(long long), INF);
for (int i = 0; i < n; i++){
dp[i][i][min(a[i], L - a[i]) <= b[i]][0] = dp[i][i][min(a[i], L - a[i]) <= b[i]][1] = min(a[i], L - a[i]);
}
for (int t = 0; t < n - 1; t++){
for (int l = n - 1; l >= 0; l--){
int r = idx(l + t);
for (int i = 0; i < n; i++){
if (dp[l][r][i][0] + dis(a[l], a[idx(l - 1)]) <= b[idx(l - 1)])
dp[idx(l - 1)][r][i + 1][0] = min(dp[idx(l - 1)][r][i + 1][0], dp[l][r][i][0] + dis(a[l], a[idx(l - 1)]));
if (dp[l][r][i][1] + dis(a[r], a[idx(l - 1)]) <= b[idx(l - 1)])
dp[idx(l - 1)][r][i + 1][0] = min(dp[idx(l - 1)][r][i + 1][0], dp[l][r][i][1] + dis(a[r], a[idx(l - 1)]));
if (dp[l][r][i][0] + dis(a[l], a[idx(r + 1)]) <= b[idx(r + 1)])
dp[l][idx(r + 1)][i + 1][1] = min(dp[l][idx(r + 1)][i + 1][1], dp[l][r][i][0] + dis(a[l], a[idx(r + 1)]));
if (dp[l][r][i][1] + dis(a[r], a[idx(r + 1)]) <= b[idx(r + 1)])
dp[l][idx(r + 1)][i + 1][1] = min(dp[l][idx(r + 1)][i + 1][1], dp[l][r][i][1] + dis(a[r], a[idx(r + 1)]));
}
for (int i = 0; i <= n; i++){
dp[idx(l - 1)][r][i][0] = min(dp[idx(l - 1)][r][i][0], dp[l][r][i][0] + dis(a[l], a[idx(l - 1)]));
dp[idx(l - 1)][r][i][0] = min(dp[idx(l - 1)][r][i][0], dp[l][r][i][1] + dis(a[r], a[idx(l - 1)]));
dp[l][idx(r + 1)][i][1] = min(dp[l][idx(r + 1)][i][1], dp[l][r][i][0] + dis(a[l], a[idx(r + 1)]));
dp[l][idx(r + 1)][i][1] = min(dp[l][idx(r + 1)][i][1], dp[l][r][i][1] + dis(a[r], a[idx(r + 1)]));
}
}
}
for (int i = n; i >= 0; i--){
for (int j = 0; j < n; j++){
if (dp[j][idx(j + n - 1)][i][0] != INF || dp[j][idx(j + n - 1)][i][1] != INF){
cout << i;
return 0;
}
}
}
return 0;
}
