#include <cstdio>
#include <cmath>
#include <cstring>
#include <cstdlib>
#include <ctime>
#include <algorithm>
#include <deque>
#include <queue>
#include <vector>
#include <map>
#include <complex>
using namespace std;
 
const int maxn=int(2e5)+100;
typedef int arr[maxn];
 
int n;
arr DFS, BFS, w, x, mat, sum, pos;
double ans;
 
void init()
{
    scanf("%d", &n);
    for (int i=1; i<=n; ++i) scanf("%d", &DFS[i]);
    for (int i=1; i<=n; ++i) scanf("%d", &BFS[i]);
    for (int i=1; i<=n; ++i) w[BFS[i]]=i;
    for (int i=1; i<=n; ++i) DFS[i]=w[DFS[i]];
    for (int i=1; i<=n; ++i) pos[DFS[i]]=i;
}
void solve()
{
    x[1]=1;
    //mat用来标记那一段是确定的
    mat[1]++; mat[2]--;
    for (int i=1; i<n; ++i)
        if (pos[i]>pos[i+1])
        {
            x[i]=1;
            mat[i]++; mat[i+1]--;
        }
    for (int i=1; i<=n; ++i) sum[i]=sum[i-1]+x[i];
    for (int i=1; i<n; ++i)
        if (DFS[i]<DFS[i+1])
        {
            if (sum[DFS[i+1]-1]-sum[DFS[i]-1])
            {
                mat[DFS[i]]++;
                mat[DFS[i+1]]--;
            }
        }
    for (int i=1, cnt=0; i<n; ++i)
    {
        cnt+=mat[i];
        if (cnt) ans+=x[i];//cnt>0说明s[i]是确定的
        else ans+=0.5;
    }
}
int main()
{
    freopen("count.in", "r", stdin);
    freopen("count.out", "w", stdout);
    init();
    solve();
    printf("%.3lf\n", ans+1.0);
    return 0;
}