#include <bits/stdc++.h>
using namespace std;
const int MAX_N = 201;
const int MAX_T = 1e9 + 1;
int x[MAX_N], t[MAX_N];
int minTimeL[MAX_N][MAX_N][MAX_N], minTimeR[MAX_N][MAX_N][MAX_N];
int main() {
int n, l;
cin >> n >> l;
x[0] = 0;
for ( int i = 1; i <= n; i++ )
cin >> x[i];
x[n + 1] = l;
t[0] = -1;
for ( int i = 1; i <= n; i++ )
cin >> t[i];
t[n + 1] = -1;
for ( int i = 0; i <= n; i++ ) {
for ( int j = 0; j <= n; j++ ) {
for ( int k = 0; k <= n; k++ )
minTimeL[i][j][k] = minTimeR[i][j][k] = MAX_T;
}
}
minTimeL[0][0][0] = minTimeR[0][0][0] = 0;
int maxStamps = 0;
for ( int i = 0; i <= n; i++ ) {
for ( int j = 0; i + j <= n; j++ ) {
for ( int k = n - 1; k >= 0; k-- ) {
if ( minTimeL[i][j][k] <= t[n + 1 - i] )
minTimeL[i][j][k + 1] = min( minTimeL[i][j][k + 1], minTimeL[i][j][k] );
if ( minTimeR[i][j][k] <= t[j] )
minTimeR[i][j][k + 1] = min( minTimeR[i][j][k + 1], minTimeR[i][j][k] );
}
for ( int k = 0; k <= n; k++ ) {
if ( minTimeL[i][j][k] < MAX_T )
maxStamps = max( maxStamps, k );
if ( minTimeR[i][j][k] < MAX_T )
maxStamps = max( maxStamps, k );
minTimeL[i + 1][j][k] = min( minTimeL[i + 1][j][k], minTimeL[i][j][k] + x[n + 1 - i] - x[n - i] );
minTimeL[i + 1][j][k] = min( minTimeL[i + 1][j][k], minTimeR[i][j][k] + x[j] + l - x[n - i] );
minTimeR[i][j + 1][k] = min( minTimeR[i][j + 1][k], minTimeL[i][j][k] + l - x[n + 1 - i] + x[j + 1] );
minTimeR[i][j + 1][k] = min( minTimeR[i][j + 1][k], minTimeR[i][j][k] + x[j + 1] - x[j] );
}
}
}
cout << maxStamps << "\n";
}
