#include <stdio.h>
#define N 200
#define INF 0x3f3f3f3f3f3f3f3fLL
long long min(long long a, long long b) { return a < b ? a : b; }
int max(int a, int b) { return a > b ? a : b; }
int dist(int m, int a, int b) {
int tmp;
if (a > b)
tmp = a, a = b, b = tmp;
return min(b - a, m + a - b);
}
int main() {
static int xx[N], tt[N];
static long long dp[N + 1][N + 1][N + 1][2];
int n, m, i, j, k, k_, s;
scanf("%d%d", &n, &m);
for (i = 0; i < n; i++)
scanf("%d", &xx[i]);
for (i = 0; i < n; i++)
scanf("%d", &tt[i]);
for (i = 0; i <= n; i++)
for (j = i; j <= n; j++)
for (k = 0; k <= n; k++)
for (s = 0; s < 2; s++)
dp[i][j][k][s] = INF;
dp[0][n][0][0] = 0;
for (i = 0; i <= n; i++)
for (j = n; j > i; j--)
for (k = 0; k <= n; k++)
for (s = 0; s < 2; s++) {
long long t = dp[i][j][k][s], t_;
int x = s == 0 ? (i == 0 ? 0 : xx[i - 1]) : (j == n ? 0 : xx[j]);
if (t == INF)
continue;
k_ = k, t_ = t + dist(m, x, xx[i]);
if (t_ <= tt[i])
k_++;
dp[i + 1][j][k_][0] = min(dp[i + 1][j][k_][0], t_);
k_ = k, t_ = t + dist(m, x, xx[j - 1]);
if (t_ <= tt[j - 1])
k_++;
dp[i][j - 1][k_][1] = min(dp[i][j - 1][k_][1], t_);
}
k_ = 0;
for (i = 0; i <= n; i++)
for (k = 0; k <= n; k++)
if (dp[i][i][k][0] != INF || dp[i][i][k][1] != INF)
k_ = max(k_, k);
printf("%d\n", k_);
return 0;
}
