RT，AC的那发是验证题解正确性的

#include <map>
#include <stack>
#include <queue>
#include <cmath>
#include <ctime>
#include <cstdio>
#include <vector>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#define D double
#define LD long double
#define LL long long
#define ULL unsigned long long
#define fi first
#define se second
#define mp make_pair
using namespace std;

bool nc[1010][1010];

char buf[1 << 23], *p1 = buf, *p2 = buf, obuf[1 << 23], *O = obuf;
#define getchar() (p1 == p2 &&(p2 = (p1 = buf) + fread(buf, 1, 1 << 21, stdin), p1 == p2) ? EOF : *p1++)

inline int rd()
{
	int x = 0, f = 1;
	char ch = getchar();
	while (!isdigit(ch))
	{
		if (ch == '-')
			f = -1;
		ch = getchar();
	}
	while (isdigit(ch))
		x = x * 10 + (ch ^ 48), ch = getchar();
	return x * f;
}

const int N = 1e5 + 7, M = 1e7 + 7;
const LL inf = 1e18;
int n, S, T, h[N], hi[N], e[M], t[M], tot, d[N];
int s[N];
LL mxf, f[M];
inline void add(int x, int y, LL z, int o = 1)
{
	e[++tot] = y, s[tot] = x, f[tot] = z, t[tot] = h[x], h[x] = tot;
	if (o)
	{
		add(y, x, 0, 0);
	}
	return;
}

inline bool bfs()
{
	for (int i = 1; i <= n; i++)
	{
		d[i] = 0;
	}
	queue<int> q;
	q.push(S), d[S] = 1;
	while (q.size())
	{
		int x = q.front();
		q.pop();
		for (int i = h[x]; i; i = t[i])
		{
			int y = e[i];
			LL z = f[i];
			if (d[y] || !z)
			{
				continue;
			}
			q.push(y);
			d[y] = d[x] + 1;
			if (y == T)
			{
				return 1;
			}
		}
	}
	return 0;
}

LL dinic(int x, LL nwf)
{
	if (x == T)
	{
		return nwf;
	}
	LL rst = nwf;
	for (int &i = hi[x]; i; i = t[i])
	{
		int y = e[i];
		LL z = f[i];
		if (d[y] != d[x] + 1 || !z)
		{
			continue;
		}
		LL k = dinic(y, min(z, rst));
		if (!k)
		{
			d[y] = 0;
		}
		else
		{
			f[i] -= k;
			f[i ^ 1] += k;
			rst -= k;
		}
		if (!rst)
		{
			break;
		}
	}
	return nwf - rst;
}

inline void Main()
{
	while (bfs())
	{
		for (int i = 1; i <= n; i++)
		{
			hi[i] = h[i];
		}
		LL now;
		while ((now = dinic(S, inf)))
		{
			mxf += now;
		}
	}
	return;
}

inline void init(int _n, int _S, int _T)
{
	n = _n, S = _S, T = _T, tot = 1, mxf = 0;
	for (int i = 1; i <= n; i++)
	{
		h[i] = 0;
	}
	return;
}


int main()
{
	int n;
	cin >> n;
	init(2 * n + 2, 2 * n + 1, 2 * n + 2);
	for (int i = 1; i <= n; i++)
	{
		int x;
		cin >> x;
		add(i + n, 2 * n + 2, x);
	}
	for (int i = 1; i <= n; i++)
	{
		int x;
		cin >> x;
		add(2 * n + 1, i, x);
	}
	int m;
	cin >> m;
	for (int i = 1; i <= m; i++)
	{
		int u, v;
		cin >> u >> v;
		nc[u][v] = 1;
	}
	for (int i = 1; i <= n; i++)
	{
		for (int j = 1; j <= n; j++)
		{
			if (i != j && !nc[i][j])
			{
				add(i, j + n, 1ll);
			}
		}
	}
	Main();
	printf("%lld\n", mxf);
	for (int i = 4 * n + 2; i <= tot; i++)
	{
		if (i % 2 == 0 && f[i] == 0)
		{
			printf("%d %d\n", s[i], e[i] - n);
		}
	}
	return 0;
}