#include<cstdio>

typedef long long ll;
template<class T>
inline void read(T&x)
{
    x=0;bool f=0;char c=getchar();
    while((c<‘0‘||c>‘9‘)&&c!=‘-‘)c=getchar(); if(c==‘-‘)f=1,c=getchar();
    while(c>=‘0‘&&c<=‘9‘){x=x*10+c-‘0‘;c=getchar();}
    x=f?-x:x;
}
const int MAXN(200010);
int B[MAXN],D[MAXN],n,D_num[MAXN],l,r,B_num[MAXN];
bool bf[MAXN];double Ans;
int main()
{
    freopen("C.in","r",stdin);
    freopen("C.out","w",stdout);
    scanf("%d",&n);
    for(int i=1;i<=n;i++)scanf("%d",&D[i]);
    for(int i=1;i<=n;i++)scanf("%d",&B[i]),B_num[B[i]]=i;
    for(int i=1;i<=n;i++)D[i]=B_num[D[i]],D_num[D[i]]=i;
    Ans=2;bf[D_num[1]]=bf[D_num[2]]==1;l=2;r=n+1;
    for(int i=3;i<=n;i++)
    {
        if(D_num[i-1]>D_num[i])Ans+=1;
        else 
        if(D_num[i-1]==D_num[i]-1&&n-r+1+l==i-1)
        {
            Ans+=0.5;
        }
        bf[D_num[i]]=1;
        while(bf[l+1])l++;
        while(bf[r-1])r--;
    }
    printf("%.3lf",Ans);
    return 0;
}