#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define fr first
#define sc second
#define clr(a, x) memset(a, x, sizeof(a))
#define dbg(x) cout<<"("<<#x<<"): "<<x<<endl;
#define printvector(arr) for (auto it = arr.begin(); it != arr.end(); ++it) cout<<*it<<" "; cout<<endl;
#define all(v) v.begin(), v.end()
#define lcm(a, b) (a * b)/__gcd(a, b)
#define int long long int
#define printvecpairs(vec) for(auto it: vec) cout<<it.fr<<' '<<it.sc<<endl;
#define endl '\n'
#define float long double
const int MOD = 1e9 + 7;
const int INF = 2e15;
const int MAXN =205;
int n, m;
int a[MAXN], b[MAXN];
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
#ifdef LOCAL
freopen("input.txt", "r", stdin);
#endif
cin>>n>>m;
for(int i= 1;i<=n;i++){
cin>>a[i];
}
for(int i= 1;i<=n;i++){
cin>>b[i];
}
int dp[n+3][n+3][n+3][2];
for(int i = 0;i<=n+1;i++){
for(int j= n+1;j>=0;j--){
for(int k = 0;k<=n+1;k++){
dp[i][j][k][0] = dp[i][j][k][1] = INF;
}
}
}
// i = ith index from right
// j = jth index from left
// k = number of taken stamps
dp[0][n+1][0][0] = 0;
dp[0][n+1][0][1] = 0;
int ans = 0;
for(int i = 0;i<n;i++){
for(int j= n+1;j>=1;j--){
if(j <= i+1) break;
for(int k = 0;k<=n;k++){
for(int p= 0;p<2;p++){
if(p == 0){
int last;
if(j == n+1) last = m;
else last = a[j];
int dist1 = a[i+1] - a[i];
int dist2 = a[i+1] + m - last;
int t1 = min(dp[i][j][k][0] + dist1, dp[i][j][k][1] + dist2);
int newk = k;
if(t1 <= b[i+1]) newk++;
dp[i+1][j][newk][0] = min(dp[i+1][j][newk][0], t1);
if(dp[i+1][j][newk][0] < INF){
ans = max(ans,newk);
}
} else {
int last;
if(j == n+1) last = m;
else last = a[j];
int dist1 = last - a[j-1];
int dist2 = a[i] + m - a[j-1];
int t2 = min(dp[i][j][k][1] + dist1, dp[i][j][k][0] + dist2);
int newk = k;
if(t2 <= b[j-1]) newk++;
dp[i][j-1][newk][1] = min(dp[i][j-1][newk][1], t2);
if(dp[i][j-1][newk][1] < INF){
ans = max(ans, newk);
}
}
}
}
}
}
cout<<ans<<endl;
return 0;
}
