//n <= 5000, subtask 1, 3, 5, 6
#include<bits/stdc++.h>
using namespace std;
int dp[5005][5005], a[5005], b[5005];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
int n; cin>>n;
for(int i = 1; i <= n; i++) cin>>a[i];
for(int i = 1; i <= n; i++) cin>>b[i];
int curmaxa = 0;
for(int i = 1; i <= n; i++){
curmaxa = max(curmaxa, a[i]);
if(a[i] == curmaxa) dp[0][i] = 0;
else dp[0][i] = -1e9;
}
for(int i = 1; i <= n; i++){
//Previous is current max of now
stack<int> value_stack, dp_stack;
for(int j = 1; j <= n; j++){
while(value_stack.size() > 0 && a[value_stack.top()] < a[j]) value_stack.pop();
if(value_stack.size() == 0 || dp[i-1][value_stack.top()] < dp[i-1][j]) value_stack.push(j);
dp[i][j] = max(dp[i][j], dp[i-1][value_stack.top()]);
}
//Now is the current max of previous
stack<pair<int, int>> dp_val_stack;
for(int j = 1; j <= n; j++){
int curmax = dp[i-1][j];
while(dp_val_stack.size() > 0 && a[dp_val_stack.top().first] <= a[j]){
curmax = max(curmax, dp_val_stack.top().second);
dp_val_stack.pop();
}
dp_val_stack.push({j, curmax});
dp[i][j] = max(dp[i][j], curmax);
}
//Update b
for(int j = 1; j <= n; j++) if(b[i] == a[j]) dp[i][j]++;
//for(int j = 1; j <= n; j++) cout<<i<<" "<<j<<" "<<dp[i][j]<<endl;
}
int ans = 0, curmax = 0;
for(int i = n; i >= 1; i--){
curmax = max(curmax, a[i]);
if(a[i] == curmax) ans = max(ans, dp[n][i]);
}
cout<<ans;
}
