#include <stdio.h>
#define N 500000
int max(int a, int b) { return a > b ? a : b; }
unsigned int X = 12345;
int rand_() {
return (X *= 3) >> 1;
}
int xx[N], yy[N];
int compare_y(int i, int j) {
return yy[i] == yy[j] ? 0 : (yy[i] < yy[j] ? -1 : 1);
}
int compare_xy(int i, int j) {
return xx[i] != xx[j] ? (xx[i] > xx[j] ? -1 : 1) : (yy[i] == yy[j] ? 0 : (yy[i] > yy[j] ? -1 : 1));
}
int (*compare)(int, int);
void sort(int *ii, int l, int r) {
while (l < r) {
int i = l, j = l, k = r, i_ = ii[l + rand_() % (r - l)], tmp;
while (j < k) {
int c = compare(ii[j], i_);
if (c == 0)
j++;
else if (c < 0) {
tmp = ii[i], ii[i] = ii[j], ii[j] = tmp;
i++, j++;
} else {
k--;
tmp = ii[j], ii[j] = ii[k], ii[k] = tmp;
}
}
sort(ii, l, i);
l = k;
}
}
int ft[N];
void update(int i, int n, int x) {
while (i < n) {
ft[i] = max(ft[i], x);
i |= i + 1;
}
}
int query(int i) {
int x = 0;
while (i >= 0) {
x = max(x, ft[i]);
i &= i + 1, i--;
}
return x;
}
int main() {
static int ii[N];
int n, h, i, x, y;
scanf("%*d%d", &n);
for (i = 0; i < n; i++)
scanf("%d", &xx[i]);
for (i = 0; i < n; i++)
scanf("%d", &yy[i]);
for (i = 0; i < n; i++) {
x = xx[i] + yy[i], y = xx[i] - yy[i];
xx[i] = x, yy[i] = y;
}
for (i = 0; i < n; i++)
ii[i] = i;
compare = compare_y, sort(ii, 0, n);
for (h = 0, y = 0; h < n; h++)
yy[ii[h]] = h + 1 == n || yy[ii[h + 1]] != yy[ii[h]] ? y++ : y;
compare = compare_xy, sort(ii, 0, n);
for (h = 0; h < n; h++) {
i = ii[h];
update(yy[i], n, query(yy[i] - 1) + 1);
}
printf("%d\n", query(n - 1));
return 0;
}
