#include <bits/stdc++.h>

typedef long long LL;

const int N = 40 + 7;
const int P = 100 + 7;
const int E = 10000 + 7;
const int S = P - 1;
const int T = P - 2;
const int INF = 0x3f3f3f3f;

int head[P], cur[P], nxt[E], to[E], fl[E], tot = 1;
int n, m, ans;
int d[P];

void add(int x, int y, int z, int w = 0) {
  nxt[++tot] = head[x], head[x] = tot, to[tot] = y, fl[tot] = z;
  nxt[++tot] = head[y], head[y] = tot, to[tot] = x, fl[tot] = w;
}

bool bfs() {
  std::queue<int> q;
  memset(d, -1, sizeof d);
  d[S] = 0, q.push(S);
  while(!q.empty()) {
    int x = q.front();
    q.pop();
    for(int i = head[x]; i; i = nxt[i])
      if(d[to[i]] == -1 && fl[i]) {
	d[to[i]] = d[x] + 1;
	q.push(to[i]);
      }
  }
  return d[T] != -1;
}

int dinic(int x, int y) {
  if(x == T)
    return y;
  int f = 0, t;
  for(int &i = cur[x]; i; i = nxt[i])
    if(d[to[i]] == d[x] + 1 && fl[i]) {
      t = dinic(to[i], std::min(fl[i], y - f));
      f += t;
      fl[i] -= t;
      fl[i ^ 1] += t;
      if(f == y)
	return y;
    }
  return f;
}

int main() {

  scanf("%d", &n);
  for(int i = 1, x, y; i <= n; ++i) {
    scanf("%d%d", &x, &y);
    ans += x + y;
    add(S, i, x);
    add(i, i + n, x + y);
    add(i + n, T, y);
  }
  scanf("%d", &m);
  for(int i = 1, x, y; i <= m; ++i) {
    scanf("%d%d", &x, &y);
    add(x + 1 + n, y + 1, INF);
  }
  
  while(bfs()) {
    memcpy(cur, head, sizeof cur);
    ans -= dinic(S, INF);
  }

  printf("%d\n", ans);

  return 0;

}