#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 2e5+2, inf = 1e18;
int dp[204][204][204][2];
void solve(){
int n, l;
cin >> n >> l;
vector<int> a(n+2), mt(n+2);
a[0] = 0; a[n+1] = l;
for(int i = 1; i <= n; i ++ )cin >> a[i];
for(int i = 1; i <= n; i ++ )cin >> mt[i];
for(int x = 0; x <= n; x ++ )
for(int y = 0; y <= n; y ++ )
for(int z = 0; z <= n; z ++ )
for(int t = 0; t < 2; t ++ )
dp[x][y][z][t] = inf;
dp[0][0][0][0] = dp[0][0][0][1] = 0;
auto po = [&](int y) -> int{
return n+1 - y;
};
auto chmin = [&](int &a, const int &b) -> void{
a = min(a, b);
return;
};
int ans = 0;
for(int z = 0; z < n; z ++ )
for(int x = 0; x < n; x ++ )
for(int y = 0; y + x < n; y ++ ){
// t == 0;
if(dp[x][y][z][0] != inf ) {
int ntim = 0;
// go further
ntim = dp[x][y][z][0] + a[x + 1] - a[x];
if(mt[x + 1] >= ntim) chmin( dp[x+1][y][z+1][0], ntim );
chmin( dp[x+1][y][z][0], ntim );
// go back
ntim = dp[x][y][z][0] + a[x] + l - a[po(y + 1)];
if(mt[po(y + 1)] >= ntim) chmin( dp[x][y+1][z+1][1], ntim );
chmin( dp[x][y+1][z][1], ntim );
}
// t == 1;
if(dp[x][y][z][1] != inf ) {
int ntim = 0;
// go further
ntim = dp[x][y][z][1] + a[po(y)] - a[po(y+1)];
if(mt[po(y + 1)] >= ntim) chmin( dp[x][y+1][z+1][1], ntim );
chmin( dp[x][y+1][z][1], ntim);
// go back
ntim = dp[x][y][z][1] + l - a[po(y)] + a[x + 1];
if(mt[x + 1] >= ntim) chmin( dp[x+1][y][z+1][0], ntim );
chmin( dp[x+1][y][z][0], ntim );
};
}
for(int z = 0; z <= n; z ++ )
for(int x = 0; x <= n; x ++ )
for(int y = 0; y <= n; y ++ )
for(int t = 0; t < 2; t ++ )
if(dp[x][y][z][t] != inf)ans = z;
cout << ans << '\n';
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);cout.tie(nullptr);
int tt = 1;
//cin >> tt;
while(tt--){
solve();
};
}
