#include <bits/stdc++.h>
using namespace std;

const int MAXN = 1e5 + 10;

int n, a[MAXN], b[MAXN], ind[MAXN];

void input() {
	cin >> n;
	for (int i = 1; i <= n; i++)
		cin >> a[i];
	for (int i = 1; i <= n; i++) {
		cin >> b[i];	
		ind[b[i]] = i;	
	}
}

void findAns() {
	vector<pair<int, int>> res;
	int mi = -1, ma = -1, x = -1;
	bool f = false;
	for (int i = 1; i <= n; i++) {
		if (!f) {
			if (a[i] == b[i]) {
				if (i != 1)
					res.push_back({a[i - 1], a[i]});
				continue;
			}
			if (a[i] > b[i]) {
				cout << "NO" << endl;
				return;	
			}
			mi = a[i];
			ma = b[i];
			x = mi;
			f = true;
			if (i != 1) {
				for (int j = i; j <= n; j++)
					res.push_back({a[i - 1], a[j]});
			}
			continue;
		}
		if (a[i] < mi || a[i] > ma) {
			if (ind[x] >= ind[a[i]]) {
				cout << "NO" << endl;
				return;	
			}
			res.push_back({x, a[i]});
		}
		if (ind[a[i]] < ind[x])
			x = a[i];
	}
	cout << res.size() << endl;
	for (auto p : res)
		cout << p.first << " " << p.second << endl;
}

int main() {
	ios::sync_with_stdio(false); cin.tie(0);
	input();
	findAns();
	return 0;	
}