#include<cstdio>

 #include<iostream>

 #include<cmath>

 #include<algorithm>

 #include<cstring>

 #include<cstdlib>

 #include<cctype>

 #include<vector>

 #include<stack>

 #include<queue>

 using namespace std;

 #define enter puts("")

 #define space putchar(' ')

 #define Mem(a, x) memset(a, x, sizeof(a))

 #define rg register

 typedef long long ll;

 typedef double db;

 const int INF = 0x3f3f3f3f;

 const db eps = 1e-;

 const int maxn = 1e5 + ;

 inline ll read()

 {

   ll ans = ;

   char ch = getchar(), last = ' ';

   while(!isdigit(ch)) {last = ch; ch = getchar();}

   while(isdigit(ch)) {ans = ans *  + ch - ''; ch = getchar();}

   if(last == '-') ans = -ans;

   return ans;

 }

 inline void write(ll x)

 {

   if(x < ) x = -x, putchar('-');

   if(x >= ) write(x / );

   putchar(x %  + '');

 }

 int n, a[maxn], pos[maxn];

 int Max[maxn];

 int c[maxn];

 int lowbit(int x)

 {

   return x & -x;

 }

 void add(int pos, int x)

 {

   for(; pos <= n && c[pos] < x; pos += lowbit(pos)) c[pos] = x;

 }

 int query(int pos)

 {

   int ret = ;

   for(; pos; pos -= lowbit(pos)) if(c[pos] > ret) ret = c[pos];

   return ret;

 }

 int main()

 {

   n = read();

   for(int i = ; i <= n; ++i) a[i] = read();

   for(int i = ; i <= n; ++i) {int x = read(); pos[x] = i;}

   for(int i = ; i <= n; ++i)

     {

       for(int j = max(, a[i] - ); j <= min(n, a[i] + ); ++j)

     Max[j] = query(pos[j] - );

       for(int j = max(, a[i] - ); j <= min(n, a[i] + ); ++j)

     add(pos[j], Max[j] + );

     }

   write(query(n)), enter;

   return ;

 }