#include <iostream>
#include <cstdio>

using namespace std;

typedef long long LL;

const int N = 200005;

int n, dfn[N], bfn[N], pos[N], d[N], b[N], c[N];

double ans;

void ins(int l, int r) {
	c[l]++, c[r + 1]--;
}

int main() {
	scanf("%d", &n);
	for (int i = 1, x; i <= n; i++) scanf("%d", &x), dfn[x] = i;
	for (int i = 1, x; i <= n; i++) scanf("%d", &x), bfn[x] = i;
	ans = 1, ins(1, 1);
	for (int i = 1; i <= n; i++) b[dfn[i]] = bfn[i];
	for (int i = 1; i <= n; i++) d[bfn[i]] = dfn[i];
	for (int i = 1; i < n; i++) {
		if (d[i] > d[i + 1]) ans++, ins(i, i);
		if (b[i] < b[i + 1] - 1) ins(b[i], b[i + 1] - 1);
	}
	for (int i = 1; i < n; i++) {
		c[i] += c[i - 1];
		if (!c[i]) ans += 0.5;
	}
	++ans;
	printf("%.3f\n", ans);
	return 0;
}