#include <bits/stdc++.h>
using namespace std;
int N, L;
long long dp[2][205][205][205];
//bool vis[2][205][205][205];
long long arr[205], brr[205];
void relax(int cw,int ccw, int k){
long long d = dp[0][cw][ccw][k]+arr[cw+1]-arr[cw];
bool kk = (d <= brr[cw+1]);
assert(d >= 0);
dp[0][cw+1][ccw][k+kk] = min(dp[0][cw+1][ccw][k+kk], d);
d = dp[1][cw][ccw][k] + L-arr[ccw] + arr[cw+1];
kk = (d <= brr[cw+1]);
assert(d >= 0);
dp[0][cw+1][ccw][k+kk] = min(dp[0][cw+1][ccw][k+kk], d);
d = dp[0][cw][ccw][k] + arr[cw] + L-arr[ccw-1];
kk = (d <= brr[ccw-1]);
assert(d >= 0);
dp[1][cw][ccw-1][k+kk] = min(dp[1][cw][ccw-1][k+kk], d);
d = dp[1][cw][ccw][k] + arr[ccw] - arr[ccw-1];
kk = (d <= brr[ccw-1]);
assert(d >= 0);
dp[1][cw][ccw-1][k+kk] = min(dp[1][cw][ccw-1][k+kk], d);
}
int main(){
cin.sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> N >> L;
for(int i = 1; i<=N; i++){
cin >> arr[i];
}
for(int i = 1; i<=N; i++){
cin >> brr[i];
}
for(int cw = 0; cw<=N; cw++){
for(int ccw = N+1; ccw>cw; ccw--){
for(int k = 0; k<=N; k++){
dp[0][cw][ccw][k] = dp[1][cw][ccw][k] = LLONG_MAX/4;
}
}
}
dp[0][0][N+1][0] = 0; //sd = 0 means cw
arr[N+1] = L;
for(int cw = 0; cw<=N; cw++){
for(int ccw = N+1; ccw>cw+1; ccw--){
for(int k = 0; k<=N; k++){
relax(cw, ccw, k);
}
}
}
int ans = 0;
for(int k = 0; k<=N; k++){
for(int cw = 0; cw<=N; cw++){
for(int ccw = N+1; ccw>cw; ccw--){
if(dp[0][cw][ccw][k] != LLONG_MAX/4){
ans = max(ans, k);
}
if(dp[1][cw][ccw][k] != LLONG_MAX/4){
ans = max(ans, k);
}
}
}
}
cout << ans;
}
