#include <bits/stdc++.h>
using namespace std;

inline int read() {
    int x = 0, f = 0; char c = 0;
    while (!isdigit(c)) f |= c == '-', c = getchar();
    while (isdigit(c)) x = (x << 3) + (x << 1) + (c & 15), c = getchar();
    return f ? -x : x;
}

#define N 1000010
int n, m, res = 0;
pair<int, int> a[N];

int main() {
	n = read(), m = read();
	for (int i = 1; i <= m; i ++) a[i].second = read();
	for (int i = 1; i <= m; i ++) a[i].first = read();

	sort(a + 1, a + m + 1);

	for (int i = 1, now = 0; i <= m; i ++) {
		if (a[i].second == 1) now ++;
		else res = max(res, a[i].first + now);
	}
	for (int i = m, now = 0; i >= 1; i --) {
		if (a[i].second == 0) now ++;
		else res = max(res, n - a[i].first + 1 + now);
	}
	printf("%d\n", res);
	return 0;
}