int main(void)
{
int N,M,res;
int u,v,c,a,b;
/* 0, N+1 represent CoreA, CoreB respectively */
scanf("%d%d",&N,&M);
V=N+2;
memset(hdr, -1, sizeof(hdr[0])*V);
for(v=1;v<=N;v++) {
scanf("%d%d",&a,&b);
connect(v, N+1, a);
connect(N+1, v, 0);
connect(0, v, b);
connect(v, 0, 0);
}
while(M--) {
scanf("%d%d%d",&u,&v,&c);
connect(u, v, c);
connect(v, u, c);
}
res=0;
while(dinicBFS()) res += dinicDFS();
printf("%d\n", res);
return 0;
}
int maxflow(int s, int t){
this->s = s, this->t = t;
int flow=0, mf;
while ( dinicBFS() ){
memset(cur,0,sizeof(cur));
while ( (mf=dinicDFS(s,INF)) )flow+=mf;
}
return flow;
}
int dinicDFS(int u, int a){
if (u==t || a==0)return a;
int flow=0, f;
for (int &i=cur[u]; i<(int)G[u].size(); i++){
Edge &e = edges[ G[u][i] ];
if (d[u]+1!=d[e.to])continue;
f = dinicDFS(e.to, min(a, e.cap-e.flow) );
if (f>0){
e.flow += f;
edges[ G[u][i]^1 ].flow -=f;
flow += f;
a -= f;
if (a==0)break;
}
}
return flow;
}