重点：构图
//最小割转网络流
//邻接表+Dinic
//Time:5797Ms Memory:6192K
#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<queue>
using namespace std;
#define MAXN 20005
#define MAXM 500005
#define INF 0x3f3f3f3f
struct Edge{
int v, w, next;
Edge(){}
Edge(int vv, int ww, int nn):v(vv), w(ww), next(nn){}
}e[MAXM];
int n,m;
int s,t;
int h[MAXN], le;
int d[MAXN];
void add(int u, int v, int w)
{
e[le] = Edge(v, w, h[u]); h[u] = le++;
}
bool bfs()
{
memset(d, -1, sizeof(d));
queue<int> q;
q.push(s); d[s] = 0;
while(!q.empty()){
int cur = q.front();
q.pop();
for(int i = h[cur]; i != -1; i = e[i].next)
{
int v = e[i].v;
if(d[v] == -1 && e[i].w)
{
d[v] = d[cur] + 1;
if(v == t) return true;
q.push(v);
}
}
}
return false;
}
int dfs(int x, int sum)
{
if(x == t || sum == 0) return sum;
int src = sum;
for(int i = h[x]; i != -1; i = e[i].next)
{
int v = e[i].v;
if(d[v] == d[x] + 1 && e[i].w){
int tmp = dfs(v, min(e[i].w, sum));
e[i].w -= tmp;
e[i^1].w += tmp;
sum -= tmp;
}
}
return src - sum;
}
int Dinic()
{
int maxFlow = 0;
while(bfs())
maxFlow += dfs(s, INF);
return maxFlow;
}
int main()
{
//freopen("in.txt", "r", stdin);
memset(h,-1,sizeof(h));
scanf("%d%d", &n,&m);
s = 0; t = n+1;
for(int i = 1; i <= n; i++)
{
int a,b;
scanf("%d%d", &a,&b);
add(s, i, a); add(i, s, 0);
add(i, t, b); add(t, i, 0);
}
for(int i = 1; i <= m; i++)
{
int u, v, w;
scanf("%d%d%d", &u, &v, &w);
add(u, v, w); add(v, u, w);
}
printf("%d\n", Dinic());
return 0;
}